itest: fix endorsement itests

diff --git a/itest/lnd_experimental_endorsement.go b/itest/lnd_experimental_endorsement.go
index 7b0fc21..67f5e30 100644
--- a/itest/lnd_experimental_endorsement.go
+++ b/itest/lnd_experimental_endorsement.go
@@ -57,12 +57,18 @@ func testEndorsement(ht *lntest.HarnessTest, aliceEndorse bool) {
 		FeeLimitMsat:   math.MaxInt64,
 	}
 
-	expectedValue := []byte{lnwire.ExperimentalUnendorsed}
-	if aliceEndorse {
-		expectedValue = []byte{lnwire.ExperimentalEndorsed}
-		t := uint64(lnwire.ExperimentalEndorsementType)
-		sendReq.FirstHopCustomRecords = map[uint64][]byte{
-			t: expectedValue,
+	var expectedValue []byte
+	hasEndorsement := lntest.ExperimentalEndorsementActive()
+
+	if hasEndorsement {
+		if aliceEndorse {
+			expectedValue = []byte{lnwire.ExperimentalEndorsed}
+			t := uint64(lnwire.ExperimentalEndorsementType)
+			sendReq.FirstHopCustomRecords = map[uint64][]byte{
+				t: expectedValue,
+			}
+		} else {
+			expectedValue = []byte{lnwire.ExperimentalUnendorsed}
 		}
 	}
 
@@ -70,8 +76,13 @@ func testEndorsement(ht *lntest.HarnessTest, aliceEndorse bool) {
 
 	// Validate that our signal (positive or zero) propagates until carol
 	// and then is dropped because she has disabled the feature.
-	validateEndorsedAndResume(ht, bobIntercept, true, expectedValue)
-	validateEndorsedAndResume(ht, carolIntercept, true, expectedValue)
+	// When the endorsement experiment is not active, no signal is sent.
+	validateEndorsedAndResume(
+		ht, bobIntercept, hasEndorsement, expectedValue,
+	)
+	validateEndorsedAndResume(
+		ht, carolIntercept, hasEndorsement, expectedValue,
+	)
 	validateEndorsedAndResume(ht, daveIntercept, false, nil)
 
 	var preimage lntypes.Preimage
diff --git a/itest/lnd_forward_interceptor_test.go b/itest/lnd_forward_interceptor_test.go
index 8eec171..615f9f4 100644
--- a/itest/lnd_forward_interceptor_test.go
+++ b/itest/lnd_forward_interceptor_test.go
@@ -432,14 +432,25 @@ func testForwardInterceptorRestart(ht *lntest.HarnessTest) {
 	// We should get another notification about the held HTLC.
 	packet = ht.ReceiveHtlcInterceptor(bobInterceptor)
 
-	require.Len(ht, packet.InWireCustomRecords, 2)
+	// Check the expected number of custom records based on whether the
+	// endorsement experiment is still active.
+	expectedLen := 1
+	if lntest.ExperimentalEndorsementActive() {
+		expectedLen = 2
+	}
+	require.Len(ht, packet.InWireCustomRecords, expectedLen)
 	require.Equal(ht, lntest.CustomRecordsWithUnendorsed(customRecords),
 		packet.InWireCustomRecords)
 
 	// And now we forward the payment at Carol, expecting only an
-	// endorsement signal in our incoming custom records.
+	// endorsement signal in our incoming custom records (if the experiment
+	// is still active).
 	packet = ht.ReceiveHtlcInterceptor(carolInterceptor)
-	require.Len(ht, packet.InWireCustomRecords, 1)
+	expectedCarolLen := 0
+	if lntest.ExperimentalEndorsementActive() {
+		expectedCarolLen = 1
+	}
+	require.Len(ht, packet.InWireCustomRecords, expectedCarolLen)
 	err = carolInterceptor.Send(&routerrpc.ForwardHtlcInterceptResponse{
 		IncomingCircuitKey: packet.IncomingCircuitKey,
 		Action:             actionResume,
diff --git a/lntest/utils.go b/lntest/utils.go
index a07b064..ab998ec 100644
--- a/lntest/utils.go
+++ b/lntest/utils.go
@@ -7,9 +7,11 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lntest/wait"
@@ -288,6 +290,15 @@ func CalcStaticFeeBuffer(c lnrpc.CommitmentType, numHTLCs int) btcutil.Amount {
 func CustomRecordsWithUnendorsed(
 	originalRecords lnwire.CustomRecords) map[uint64][]byte {
 
+	if !ExperimentalEndorsementActive() {
+		// Return nil if there are no records, to match wire encoding.
+		if len(originalRecords) == 0 {
+			return nil
+		}
+
+		return originalRecords.Copy()
+	}
+
 	return originalRecords.MergedCopy(map[uint64][]byte{
 		uint64(lnwire.ExperimentalEndorsementType): {
 			lnwire.ExperimentalUnendorsed,
@@ -295,6 +306,12 @@ func CustomRecordsWithUnendorsed(
 	)
 }
 
+// ExperimentalEndorsementActive returns true if the experimental endorsement
+// window is still open.
+func ExperimentalEndorsementActive() bool {
+	return time.Now().Before(lnd.EndorsementExperimentEnd)
+}
+
 // LnrpcOutpointToStr returns a string representation of an lnrpc.OutPoint.
 func LnrpcOutpointToStr(outpoint *lnrpc.OutPoint) string {
 	return fmt.Sprintf("%s:%d", outpoint.TxidStr, outpoint.OutputIndex)