I'm generally really bad with re-watching series since I pretty much remember everything and anything that happens in the show (outside of word-for-word dialogue).
Despite that, I've seen Code Geass (and R2) about 6 times, Prince of Tennis (yes, all 178 episodes) 4 times, and Naruto (plus Shippuuden) 5 times.
I loved Death Note and would love to watch it again, but there just isn't that epic feeling to it like the first time, even more so since I remember eerything that happened in it, despite it being about 7 months since I last watched an episode of it...