In general, moving a time-consuming operation like writing to a database out of your main thread will get the response back to the user more quickly. This may be a few thousandths of a second, so profile the app to make sure it's worth the trouble.
Are all the applications in the same JVM? I'm not sure that's going to matter, but it's interesting.
Are they in a servlet container or EJB container or something else? EJB and maybe servlet specs tell you not to spawn your own threads, but most containers have some custom, not quite standard way to do it.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi