[wyclif]

My wife has a coveted three-letter username, and recently tweeted for the first time in almost five years. That's right: for almost five years the account was completely unused, and Twitter did nothing. I think that's the right way to handle things.

So Twitter may remove accounts, and I know this is anecdotal and one data point is meaningless, but from observing this and other accounts it seems they rarely remove accounts for no activity. Unless, of course, it's trademarked.