I have 78 friends. I'll only remove them If they haven't been on for at least a month. Then I'll suspect they died. But if they're a very close friend, I'll still give them 2 months. Extremely rarely, also, I might go a year. Which I've only done once. And on that year too, a funny thing happened. Just as I was about to remove the person who was inactive for a year, The Xbox guide popped up saying they were online.