Erm ... no.
The belts will deteriorate with age, regardless of whether you run the engine or not. I have a mate with a '97 916 and he'd not managed to get out on his bike for an entire year (workaholic!), so it needed a major service before being ridden. Fortunately he had the sense to get it fetched in a van rather than ride it in because after 3 years the belts were crazed and perished.
Having said that, it doesn't get to 2 years then suddenly fall apart either. They do that pretty much continuously anyway! (joke - I think).
[Edited on 21-11-2005 by HW]