‘Elephant’ was great, but I just watched a couple of months ago so my second viewing of it is not going to be soon. I usually wait a a year or two if not more.
About your concern of it diminishing impact of repetitive viewings, it can depend greatly. For example my favorite film of all time is ‘The Godfather Pt. II’ and the first time it absolutely blew me out the water. I just watched it again after about 5 years on the new restored BD and I can say it was not the same since I knew what was going to happen but I didn’t lower it on my list because I will never ever forgive how much impact it had on me the first time I watched it.