I haven't had much lung trouble, and I've been a regular smoker for a long time. I think it's just because I inhale and exhale quickly, rather than hold it in for 30 seconds. It still gets you high, holding it in is kind of useless.

Memory's definitely something that will go. Short-term memory, anyway. It's not as bad as some grizzly old hippies make you think, though. Just that little things will slip your mind--where'd I put my keys, was I supposed to call someone, etc. It's not like you turn into a drooling tard.

I haven't noticed the sleep thing at all, though. Are you on other drugs or medications? If anything, smoking a lot makes me sleep more.