I've had three total ELs between the five sites I contribute to (IS, DT, FT, 123 and SS). One at DT which earned me $20 (woohoo!) and two at FT last Monday which netted me $6.60 each. I have between 80-150 images on each of those sites so take that as you may. But yeah there is no reason I can see not to offer ELs, you're only increasing your earnings on files you've already taken the time to keyword, categorize and submit. Just don't expect an overwhelming amount of them unless you have a huge portfolio.
