Mike, it's your imagination
The interval has not changed, but your brain is no more sensitivite to it... Besides, you don't have to read the message because you already know what it says anyway... 
Actually the seond part isn't quite true, especially if I'm busy with something else -- the two popups are quite similar in appearance, and one says the definitions update has been done for me while the other wants action on my part to load the program update.
Hmm, a thought for future versions -- maybe different colors for the auto-update-done and update-available popups?
But I'll accept that the timing's still the same, if you say so -- brain injury
does do weird things to perception
and imagination.
