Going over dreams in detail is a great way to cement them in memory. I too will usually spend upwards of 30 minutes going over and over the dreams in the morning (or even at each waking, tempered by my drowsiness, don't want to risk insomnia!). I started doing this at first to make sure I'd capture all the dreams (I recall a fairly large of scenes on most wakings and sometimes there are so many different scenes that it takes 20-30 minutes just to sort it all out) before reaching for my voice recorder. I also have experimented with maintaining a mental running list of keywords I add to all through the night on each waking, and only recording in the morning. This works well sometimes, and not so well sometimes.

But the thing about writing them down is that you have them forever. Some people who did only keyword journaling found that going back a few years later, the keywords were meaningless and the dreams were gone...