l2geth: shorter default timestamp refresh (#531)

* l2geth: set default timestamp refresh threshold to 3 mins

* l2geth: add changeset

.changeset/slimy-rocks-exist.md

+---
+"@eth-optimism/l2geth": patch
+---
+
+Set default timestamp refresh threshold to 3 minutes

l2geth/cmd/utils/flags.go

@@ -846,7 +846,7 @@ var (
 	RollupTimstampRefreshFlag = cli.DurationFlag{
 		Name:   "rollup.timestamprefresh",
 		Usage:  "Interval for refreshing the timestamp",
-		Value:  time.Minute * 15,
+		Value:  time.Minute * 3,
 		EnvVar: "ROLLUP_TIMESTAMP_REFRESH",
 	}
 	// Flag to enable verifier mode

l2geth/rollup/sync_service.go

@@ -75,8 +75,8 @@ func NewSyncService(ctx context.Context, cfg Config, txpool *core.TxPool, bc *co
 	}
 	timestampRefreshThreshold := cfg.TimestampRefreshThreshold
 	if timestampRefreshThreshold == 0 {
-		log.Info("Sanitizing timestamp refresh threshold to 15 minutes")
-		timestampRefreshThreshold = time.Minute * 15
+		log.Info("Sanitizing timestamp refresh threshold to 3 minutes")
+		timestampRefreshThreshold = time.Minute * 3
 	}
 
 	// Layer 2 chainid