I just had a marathon like this last year except I didn't have DOTM yet. I didn't get the Transformers movies on DVD until last year for some odd reason and this year I got DOTM early in a two DVDs for one deal (the other DVD was Fast Five). I still did have a TF movie marathon the day I got DOTM.
Me and my folks are doing a Harry Potter marathon. We saw the first one and we plan on watching one every day form New year up until Christmas (orthodox Christmas in on 7th January). I always love Christmas movies marathons