The main problem with the shelf life of desserts isn't them going off, its with them going stale. The reason there's so much extra crap in store bought things is to keep them moist and fresh tasting. Cream, fruit etc will definitely spoil early but muffins, cakes, brownies, pastry etc will go stale well before they go off. The fat content and the sugar actually work to preserve the product more than hamper it.
Main question would be why the question?? If you're keen to make bigger batches of things and keep them for a while I'd look to the fridge and freezer. You can freeze down cakes/brownies etc and they come out ok, fridge or freeze pastry (cooked and uncooked) and it'll still work, flour's pretty durable!
What are you hoping to make???