Fun > Story > Rules
If you think it will be fun and/or add to the story. Do it.
On a related note: What do you guys think I should do about treasure? The adventure I'm planning on running has some treasure in it, but obviously if I'm running it as a sort of dream, then the treasure might not be real. I thought maybe one magic item could be real, in that it appears in the elf PC's hands when he "wakes up", but the rest wouldn't. Should I let them collect fake treasure, or just not include it in the first place so they don't get confused?
Elves don't sleep, and they are immune to things like the dream spell ... but can they still have like prophetic visions and "waking dreams" while trancing? I ask because I had this neat idea for a sort of dream sequence quest for the elf PC in one of my campaigns, but then I remembered that elves don't sleep and don't really dream (other than their meditative exercises or whatever).
Anyone got any thoughts on the matter?