There's no way that I'm going to spend £££'s on buying DVD's and Blu-Rays and only watching them once! So just about every anime I own has been watched at least twice, and some much more than twice, and the few that haven't been watched twice because they're too new will eventually get watched again!
There are a few however that I regularly watch at least once every year such as Clannad, The Place Promised in Our Early Years and Laputa Castle in the Sky actually some of those might get watched more than once a year . Other candidates for regular re-watches include Kanon, Magic Knight Rayearth, Love Chunibyo & Other Delusions, Starship Operators and Gunslinger Girl.
I do know all that jazz. Up until 5 years ago I had very little time to watch anime, but now I'm retired and living on my own I'm making up for it.