I have gone at least a week waiting for good weather with a charged up lipo. Actually holding their charge is one of the "pluses" of a Lipo.
That being said, leaving the Lipo fully charged for a "long" time ("long" not being well defined, but maybe starting at a week in length) is considered a form of Lipo abuse! Apparently they tend to age faster. So if I know I won't be flying for a week or more, I'll discharge (slowly) my pack to roughly 1/2 capacity.
For really long periods--like over winter when you aren't going to fly at all, the current "best practice" is to discharge (or charge) to 1/2 capacity and refrigerate (not freeze!) in a sealed plastic bag--trying to keep condensation to a minimum. Then when you are ready to fly again, let them warm up in the bag, and then charge and go fly!
This like I said is considered to be the proper way to treat your lipo. I think there is some science behind it. It is also the reason, I think, that you get your lipos from the distributer at 1/2 capacity.