On the 737 we fly them at 1500' AAL, and we don't usually clean up completely, but stay at 180kts with flap 5 (2nd stage of flap). Then gear comes down with next stage of flap abeam the threshold (150kts). Then during base through to final flap and finals speed (120-140kts, depending on weight).
They're only flown once in the real aircraft, as part of the typerating. Minimum of 6 touch'n'goes I believe, but not sure.
After that they're not really done anymore, the only thing is a circling approach every year in the sim for license renewal. It's not a proper circuit but comes close.
As for fuel, usually 4-6 people are done in one flight, so the first one will have a heavy fuel load, and the last one will be the light one.
Hope this helps.