These days I wouldn't even bother with affs. Most affs with large traffic are happy with their current sponsor/s & would prolly only do prepayed traffic deals.
The old 20/80 rule still applys as well. that 20% of your affs send 80% of the sales. Meaning you'd be wasting ur time most likely running board comps and crap like that, ending up with hundreds of yoyo's buggin you daily.
Imo I'd rather spend the add budget on inhouse traffic and inhouse grunt workers then comps, but that's just me.
-N