I think you'll find that even with "global use", there are plenty of dead-time to do updates in.
We don't update ClarionShop a lot, but when we do we usually don't think too hard about it. Just wait till early morning, see if anyone is connected, and if not just stop it for a few minutes.
NT6 has a couple features which are leaning towards making this easier. The performance monitor control template let's you see easily how many current sessions there are. Also a large array of "traffic" is being created as the program runs, so with some creative graphing you should be able to identify the best times. I still need to do an example of the creative bit, but the data is being collected (into ram at this stage.)
cheers
Bruce