diff --git a/main.go b/main.go
index dbfce3b01..5771d2e15 100644
--- a/main.go
+++ b/main.go
@@ -65,7 +65,7 @@ func main() {
 
 	ruleResults := make(chan *rules.Result, 4096)
 
-	ast.SetPersistence(persistence)
+	ast.SetPersistence(persistence, nil)
 	ruleManager := rules.NewRuleManager(ruleResults, conf.Global.EvaluationInterval)
 	err = ruleManager.AddRulesFromConfig(conf)
 	if err != nil {
diff --git a/rules/ast/ast.go b/rules/ast/ast.go
index 59f9f4e79..6fc589d65 100644
--- a/rules/ast/ast.go
+++ b/rules/ast/ast.go
@@ -316,7 +316,7 @@ func (node *VectorAggregation) Eval(timestamp *time.Time) Vector {
 }
 
 func (node *VectorLiteral) Eval(timestamp *time.Time) Vector {
-	values, err := persistence.GetValueAtTime(node.labels, timestamp, &stalenessPolicy)
+	values, err := persistenceAdapter.GetValueAtTime(node.labels, timestamp)
 	if err != nil {
 		log.Printf("Unable to get vector values")
 		return Vector{}
@@ -504,7 +504,7 @@ func (node *MatrixLiteral) Eval(timestamp *time.Time) Matrix {
 		OldestInclusive: timestamp.Add(-node.interval),
 		NewestInclusive: *timestamp,
 	}
-	values, err := persistence.GetRangeValues(node.labels, interval, &stalenessPolicy)
+	values, err := persistenceAdapter.GetRangeValues(node.labels, interval)
 	if err != nil {
 		log.Printf("Unable to get values for vector interval")
 		return Matrix{}
@@ -517,7 +517,7 @@ func (node *MatrixLiteral) EvalBoundaries(timestamp *time.Time) Matrix {
 		OldestInclusive: timestamp.Add(-node.interval),
 		NewestInclusive: *timestamp,
 	}
-	values, err := persistence.GetBoundaryValues(node.labels, interval, &stalenessPolicy)
+	values, err := persistenceAdapter.GetBoundaryValues(node.labels, interval)
 	if err != nil {
 		log.Printf("Unable to get boundary values for vector interval")
 		return Matrix{}
diff --git a/rules/ast/persistence_bridge.go b/rules/ast/persistence_adapter.go
similarity index 61%
rename from rules/ast/persistence_bridge.go
rename to rules/ast/persistence_adapter.go
index 1ccd53354..36f634413 100644
--- a/rules/ast/persistence_bridge.go
+++ b/rules/ast/persistence_adapter.go
@@ -1,32 +1,23 @@
 package ast
 
-//////////
-// TEMPORARY CRAP FILE IN LIEU OF MISSING FUNCTIONALITY IN STORAGE LAYER
-//
-// REMOVE!
-
 import (
+	"flag"
 	"github.com/matttproud/prometheus/model"
 	"github.com/matttproud/prometheus/storage/metric"
 	"time"
 )
 
-// TODO ask matt about using pointers in nested metric structs
+var defaultStalenessDelta = flag.Int("defaultStalenessDelta", 300, "Default staleness delta allowance in seconds during expression evaluations.")
 
-// TODO move this somewhere proper
-var stalenessPolicy = metric.StalenessPolicy{
-	DeltaAllowance: time.Duration(300) * time.Second,
-}
-
-// TODO remove PersistenceBridge temporary helper.
-type PersistenceBridge struct {
-	persistence metric.MetricPersistence
+type PersistenceAdapter struct {
+	persistence     metric.MetricPersistence
+	stalenessPolicy *metric.StalenessPolicy
 }
 
 // AST-global persistence to use.
-var persistence *PersistenceBridge = nil
+var persistenceAdapter *PersistenceAdapter = nil
 
-func (p *PersistenceBridge) getMetricsWithLabels(labels model.LabelSet) ([]*model.Metric, error) {
+func (p *PersistenceAdapter) getMetricsWithLabels(labels model.LabelSet) ([]*model.Metric, error) {
 	fingerprints, err := p.persistence.GetFingerprintsForLabelSet(&labels)
 	if err != nil {
 		return nil, err
@@ -42,14 +33,14 @@ func (p *PersistenceBridge) getMetricsWithLabels(labels model.LabelSet) ([]*mode
 	return metrics, nil
 }
 
-func (p *PersistenceBridge) GetValueAtTime(labels model.LabelSet, timestamp *time.Time, stalenessPolicy *metric.StalenessPolicy) ([]*model.Sample, error) {
+func (p *PersistenceAdapter) GetValueAtTime(labels model.LabelSet, timestamp *time.Time) ([]*model.Sample, error) {
 	metrics, err := p.getMetricsWithLabels(labels)
 	if err != nil {
 		return nil, err
 	}
 	samples := []*model.Sample{}
 	for _, metric := range metrics {
-		sample, err := p.persistence.GetValueAtTime(metric, timestamp, stalenessPolicy)
+		sample, err := p.persistence.GetValueAtTime(metric, timestamp, p.stalenessPolicy)
 		if err != nil {
 			return nil, err
 		}
@@ -61,7 +52,7 @@ func (p *PersistenceBridge) GetValueAtTime(labels model.LabelSet, timestamp *tim
 	return samples, nil
 }
 
-func (p *PersistenceBridge) GetBoundaryValues(labels model.LabelSet, interval *model.Interval, stalenessPolicy *metric.StalenessPolicy) ([]*model.SampleSet, error) {
+func (p *PersistenceAdapter) GetBoundaryValues(labels model.LabelSet, interval *model.Interval) ([]*model.SampleSet, error) {
 	metrics, err := p.getMetricsWithLabels(labels)
 	if err != nil {
 		return nil, err
@@ -70,7 +61,7 @@ func (p *PersistenceBridge) GetBoundaryValues(labels model.LabelSet, interval *m
 	sampleSets := []*model.SampleSet{}
 	for _, metric := range metrics {
 		// TODO: change to GetBoundaryValues() once it has the right return type.
-		sampleSet, err := p.persistence.GetRangeValues(metric, interval, stalenessPolicy)
+		sampleSet, err := p.persistence.GetRangeValues(metric, interval, p.stalenessPolicy)
 		if err != nil {
 			return nil, err
 		}
@@ -85,7 +76,7 @@ func (p *PersistenceBridge) GetBoundaryValues(labels model.LabelSet, interval *m
 	return sampleSets, nil
 }
 
-func (p *PersistenceBridge) GetRangeValues(labels model.LabelSet, interval *model.Interval, stalenessPolicy *metric.StalenessPolicy) ([]*model.SampleSet, error) {
+func (p *PersistenceAdapter) GetRangeValues(labels model.LabelSet, interval *model.Interval) ([]*model.SampleSet, error) {
 	metrics, err := p.getMetricsWithLabels(labels)
 	if err != nil {
 		return nil, err
@@ -93,7 +84,7 @@ func (p *PersistenceBridge) GetRangeValues(labels model.LabelSet, interval *mode
 
 	sampleSets := []*model.SampleSet{}
 	for _, metric := range metrics {
-		sampleSet, err := p.persistence.GetRangeValues(metric, interval, stalenessPolicy)
+		sampleSet, err := p.persistence.GetRangeValues(metric, interval, p.stalenessPolicy)
 		if err != nil {
 			return nil, err
 		}
@@ -108,8 +99,14 @@ func (p *PersistenceBridge) GetRangeValues(labels model.LabelSet, interval *mode
 	return sampleSets, nil
 }
 
-func SetPersistence(p metric.MetricPersistence) {
-	persistence = &PersistenceBridge{
-		persistence: p,
+func SetPersistence(persistence metric.MetricPersistence, policy *metric.StalenessPolicy) {
+	if policy == nil {
+		policy = &metric.StalenessPolicy{
+			DeltaAllowance: time.Duration(*defaultStalenessDelta) * time.Second,
+		}
+	}
+	persistenceAdapter = &PersistenceAdapter{
+		persistence:     persistence,
+		stalenessPolicy: policy,
 	}
 }
diff --git a/rules/rules_test.go b/rules/rules_test.go
index 1893e34ec..b9e9c3bbe 100644
--- a/rules/rules_test.go
+++ b/rules/rules_test.go
@@ -173,7 +173,7 @@ func TestExpressions(t *testing.T) {
 	}()
 
 	storeMatrix(persistence, testMatrix)
-	ast.SetPersistence(persistence)
+	ast.SetPersistence(persistence, nil)
 
 	for _, exprTest := range expressionTests {
 		expectedLines := annotateWithTime(exprTest.output)