i think i see what he means, it could screw up the process in witch your brain does all the nuero-repair and such, but its not really unhealthy if you have a nap of the same leangth every day around the same time cause your brain will get used to the routine and get things done, but if your just randomly taking naps all the time of random time variations i could see possible problems.

I think that if you were to take small naps and acumalated a certain number of hours without staying awake for TO long then yeah you might have that leangthy dream. but if you were to stay awake for to long, like say a couple hour, i think your brain would start the cycle over. but im no expert on dream cycles, that just my opinion.

Peace