I register my service with the lookup server using the register() method of ServiceRegistrar.

The lease timeout that you specify when you join the lookup service is only a request - the lookup service is free to grant the lease for any amount of time up to what you request. In particular, Sun's implementation of the lookup service, reggie, won't give you a lease for more than 5 minutes. If your service needs to live longer than that, you should periodically renew the lease. The easiest way to do this is to either register your services using JoinManager or use LeaseRenewalManager.