After playing 20 years of GW games (40k V1 to V5, Space marine then netepic, Space Hulk, BFG, Man O War etc...), now I'm adding a non GW army to my collection (yeah I'm an Heretic now

).
I've read the rules, they're clear and 40k look a like, seems easy but more realistic, looks like a good cross between fun & realism to me (the recent 40k have a lot of crappy rules for realism purposes).
So, I've bought a crate of mini, I'm reading WWII books to know how to paint them in the accurate schemes, and now, the questions:
-What's the typical size of a game which last a good afternoon (something like 4h00)?
In Epic/40k etc, I'm really bored with standard games, in general i play more 3000 points 40k or 5000 points Netepic, that allows players to field lots of options.
-What are the good addresses to buy things to build a cool table? I need tons of hedges for bocage and Ambush

I already know timecast & Jr Miniatures, but if you've got others, share it !

-what are the beginners mistake? (in army list, general tactics etc). Or any general advices.
Thanks in advance !