It says on the admin screen here that we’re allowed 3,072 MB for our individual spaces here at WordPress.com, which is a pretty fair amount of space when you get right down to it.
Now my days are numbered okay, everyone’s days are numbered, but I suspect my number is lower than most and I’ve pondered the possibility of porting my Main Site, which is largely WordPress but self-hosted, over here at some point, mainly because I can’t reasonably expect my descendants to maintain (and pay for) that site. About 8,000 items that aren’t in a WordPress environment would of necessity have to be sacrificed. Still, that leaves about 14,000 posts and a handful of pages, which could be done in well, last time I had to do an import into WordPress, it took about a week for about a third as much material.
And of those three gigabytes, I’d use up two pretty quick. Then again, it’s not like I expect to make a whole lot of posthumous posts.