public Builder mergeTtl(com.google.protobuf.Duration value) {
      if (ttlBuilder_ == null) {
        if (((bitField0_ & 0x00000002) != 0)
            && ttl_ != null
            && ttl_ != com.google.protobuf.Duration.getDefaultInstance()) {
          getTtlBuilder().mergeFrom(value);
        } else {
          ttl_ = value;
        }
      } else {
        ttlBuilder_.mergeFrom(value);
      }
      if (ttl_ != null) {
        bitField0_ |= 0x00000002;
        onChanged();
      }
      return this;
    }
<pre>
Optional. TTL for the backup to expire. Value range is 1 day to 100 years.
If not specified, the default value is 100 years.
</pre>

<code>.google.protobuf.Duration ttl = 2 [(.google.api.field_behavior) = OPTIONAL];</code>
java-valkey/proto-google-cloud-valkey-v1/src/main/java/com/google/cloud/memorystore/v1/BackupInstanceRequest.java