diff --git a/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscribeTransform.java b/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscribeTransform.java
index b9f635f84..dd9675e0e 100644
--- a/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscribeTransform.java
+++ b/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscribeTransform.java
@@ -43,8 +43,6 @@
 import org.joda.time.Duration;
 
 class SubscribeTransform extends PTransform<PBegin, PCollection<SequencedMessage>> {
-  private static final Duration MAX_SLEEP_TIME = Duration.standardMinutes(1);
-
   private final SubscriberOptions options;
 
   SubscribeTransform(SubscriberOptions options) {
@@ -90,7 +88,7 @@ private RestrictionTracker<OffsetRange, OffsetByteProgress> newRestrictionTracke
         initial,
         options.getBacklogReader(subscriptionPartition.partition()),
         Stopwatch.createUnstarted(),
-        MAX_SLEEP_TIME.multipliedBy(3).dividedBy(4),
+        options.minBundleTimeout(),
         LongMath.saturatedMultiply(options.flowControlSettings().bytesOutstanding(), 10));
   }
 
@@ -136,7 +134,8 @@ public PCollection<SequencedMessage> expand(PBegin input) {
     return subscriptionPartitions.apply(
         ParDo.of(
             new PerSubscriptionPartitionSdf(
-                MAX_SLEEP_TIME,
+                // Ensure we read for at least 5 seconds more than the bundle timeout.
+                options.minBundleTimeout().plus(Duration.standardSeconds(5)),
                 this::newInitialOffsetReader,
                 this::newRestrictionTracker,
                 this::newPartitionProcessor,
diff --git a/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscriberOptions.java b/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscriberOptions.java
index 066c331b4..69757efe8 100644
--- a/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscriberOptions.java
+++ b/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/SubscriberOptions.java
@@ -42,6 +42,7 @@
 import java.io.Serializable;
 import java.util.Set;
 import org.checkerframework.checker.nullness.qual.Nullable;
+import org.joda.time.Duration;
 
 @AutoValue
 public abstract class SubscriberOptions implements Serializable {
@@ -51,6 +52,8 @@ public abstract class SubscriberOptions implements Serializable {
 
   private static final long MEBIBYTE = 1L << 20;
 
+  private static final Duration MIN_BUNDLE_TIMEOUT = Duration.standardMinutes(1);
+
   public static final FlowControlSettings DEFAULT_FLOW_CONTROL =
       FlowControlSettings.builder()
           .setMessagesOutstanding(Long.MAX_VALUE)
@@ -69,6 +72,14 @@ public abstract class SubscriberOptions implements Serializable {
    */
   public abstract Set<Partition> partitions();
 
+  /**
+   * The minimum wall time to pass before allowing bundle closure.
+   *
+   * <p>Setting this to too small of a value will result in increased compute costs and lower
+   * throughput per byte. Immediate timeouts (Duration.ZERO) may be useful for testing.
+   */
+  public abstract Duration minBundleTimeout();
+
   /**
    * A factory to override subscriber creation entirely and delegate to another method. Primarily
    * useful for testing.
@@ -95,7 +106,10 @@ public abstract class SubscriberOptions implements Serializable {
 
   public static Builder newBuilder() {
     Builder builder = new AutoValue_SubscriberOptions.Builder();
-    return builder.setPartitions(ImmutableSet.of()).setFlowControlSettings(DEFAULT_FLOW_CONTROL);
+    return builder
+        .setPartitions(ImmutableSet.of())
+        .setFlowControlSettings(DEFAULT_FLOW_CONTROL)
+        .setMinBundleTimeout(MIN_BUNDLE_TIMEOUT);
   }
 
   public abstract Builder toBuilder();
@@ -188,6 +202,8 @@ public abstract static class Builder {
 
     public abstract Builder setFlowControlSettings(FlowControlSettings flowControlSettings);
 
+    public abstract Builder setMinBundleTimeout(Duration minBundleTimeout);
+
     // Used in unit tests
     abstract Builder setSubscriberFactory(SubscriberFactory subscriberFactory);
 
diff --git a/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/Uuid.java b/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/Uuid.java
index b3ff52f54..1ddf6bd37 100644
--- a/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/Uuid.java
+++ b/pubsublite-beam-io/src/main/java/com/google/cloud/pubsublite/beam/Uuid.java
@@ -20,6 +20,7 @@
 import com.google.protobuf.ByteString;
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.util.Base64;
 import java.util.UUID;
 import org.apache.beam.sdk.coders.DefaultCoder;
 
@@ -48,6 +49,9 @@ public static Uuid random() {
     } catch (IOException e) {
       throw new RuntimeException("Should never have an IOException since there is no io.", e);
     }
-    return Uuid.of(output.toByteString());
+    // Encode to Base64 so the random UUIDs are valid if consumed from the Cloud Pub/Sub client.
+    return Uuid.of(
+        ByteString.copyFrom(
+            Base64.getEncoder().encode(output.toByteString().asReadOnlyByteBuffer())));
   }
 }