I don't have personal first hand experience with Zyprexa, but my husband has been on it (generic name Olanzapine) and I'm sorry to say but the sleepiness does not go away. He takes his early in the evening but he's sleeping within 1-1.5 hrs. He has to take it by 8pm latest so that he can get up in the mornings - if he doesn't have to get up the next day then he'll slack a little and take it at like 9 or 10 (i think he does it so that he can sleep in on Saturdays!! tee hee - he doesn't realize that i'm on to him!! haha )
He is now on 20mg of Zyprexa and it doesn't make him MORE sleepy that i've noticed but definately makes him go to bed. When he was in the midst of a (what i know now as) crazy phase (sorry, what i call it!!) I used to start bugging him to take his pills at dinner time so that the urge to take off was not able to show it's ugly face because he was asleep by 8. Nights are hardest for him so in a sense (for me anyways) they are a Godsend!!
I was on Zyprexa for a while, and I broke out in hives all over my body. Thankfully they went away after I discontinued med. I tried several mood stabilizers before I found one that is working well for me so far. Right now I am on Risperdal. Everyone reacts differently to meds, I guess that is why most BP's have to try different ones until you find the one that helps the most with the least side effects.
Good luck to your husband and if it does not work, don't let him give up! Like last night, I felt so good and relaxed and I thought well that's it, I am not taking any more meds. When I woke up this morning I realized that thought was coming from my BP brain and not the voice of reason.