but leaving the box in D is less likely to wear it out the keep selecting N or P ....thats just my opinion of course.
Mine too

After all, if you think about it:
The brake bands are 'always' in use - but they only see significant wear when changing gear (when they have to brake one or more planetary gear sets). When you're sat in D they're not really being worn (unless they are already slipping, in which case you're on borrowed time anyway), but going D-N-D they'll see some wear - granted not much, really, because;
If you think about the torque convertor - especially with a loosely coupled convertor as in the Omega - how much energy do you think it's dissipating into the oil etc through slipping the torque of the engine at idle? Especially compared to how much torque it's having to (hydraulically) transmit when you've got your hoof welded to the shag pile!
So, that's my take on it

Though I stick the handbrake on as I said earlier, because I know I hate being blinded by the person in front of me..
I'll stick it in N or P if I'm going to be stopped more than a minute or so (a regular light change), however.