Well, I can’t realy state my sources, but I have seen an article lately claiming that a 90 minutes nap during the afternoon improves your long term memory.
Now, we all know that Naps consist mainly of REM sleep. So, what if we hurt long-term memory while LD-ing? Or even more interesting, what if we selectively archive memories, instead of randomly archiving them?
Napping during the day isn’t a good idea. I’ve heard that its unhealthy for your body.
en.wikipedia.org/wiki/Power_nap#Benefits
en.wikipedia.org/wiki/Siesta#Bio … d_for_naps
The other nap articles refer to polyphasic sleep and uberman sleep schedule, which is not relevant to this topic.
In both article I couldn’t see anything obvious that said that naps are harmful. Personally I can’t see any reason why taking a nap would be harmful. Daytime tiredness can be a symptom of various ailments but that doesn’t mean the NAP itself is harmful or that the want for a nap implies an ailment.
I don’t know whether or not it improves memory, but I know everyday I get tired enough (90% of the time, doesn’t seem to matter too much to the amount of sleep I got the night before) to want to take a nap, and when I do I feel great when I wake up. (And sad that I just lost 2 hours of the day 
)
That is all from the Wikipedia_Ferret 
Does LDing interfere with REM in the first place? I thought it doesn’t. And I’m an advocate of napping no matter what. In fact, I’m going to take one right now. 
I nap sometimes too, usually after coming home from school and doing homework. At that time I’m usually tired and after a nap (let’s say 3-4 hours, I’m an extreme sleeper 
) I feel great.