Well, maybe. It somewhat depends on what your timer code does. Obviously if every 15 seconds the timer performs a 5 second task, the user is going to notice that. The timer code won’t interrupt the user, but when the timer code is running, the user won’t be able to do anything either, in other words the user can’t interrupt the timer code. Panorama only can do one thing at a time.
The Panorama X Server Administration window, which you haven’t seen yet, periodically checks the server and refreshes the status display. It uses a timer like you are planning to. It’s set up so that you can specify how often the refresh is and whether or not it continues refreshing in the background. I’ve found that I usually leave the background refresh off, because if I click on a menu at the exact time the timer goes off, it may not work (because the other database is temporarily active). Not a huge deal, I just have to click on the menu again, but it’s a bit of a "what just happened – oh, right’ sensation. This doesn’t happen very often, but enough that it bugged me. On the other hand, if I do want background refresh, I want it frequent so I set it to every second. If you are only doing it every 15 seconds it should be much less noticeable. Also, you won’t be doing network activity in your timer, so it may be faster/less noticeable. Basically, I think the only way you’ll know for sure is to try it.