My lips get a bit numb after an hour of practice.......I'm trying too hard aren't I.

There is a very good chance of that, there is that slight chance that your lips are just sensitive, remember to try to stay relaxed when practicing, that means not only your whole body but also your breathing, be sure your breathing is coming from very deep and not just from your mouth, if trying to blow and draw just from your mouth you will find that you are tightening up you jaw and lips and probably running out of air to soon.

My wife has complained of numb lips after so long...

Thanks Yukon. I try to relax, I really do but it don't come easy(now there's a tune). Sometimes I can do it. I'm hoping it will all come together with practice. That's the other thing, I practise every day but its hard to get that truly alone time with a family of 5. But that's when (sometimes) it all happens. I love those moments.
Overblow, I have a special 20 with ABS comb so the whisky's not a problem. Which is a good thing.
Gene, I'm assuming your wife's not blowin a harp. You lucky bugger.

possibly just the vibrations, there is nothing to worry about here. maybe you have sensitive lips, but thats not bad. anyway what i just said! no worries here!