trouble with mine are they are all in very competitive markets - the
SEO is growing but there are a lot of established domains doing the same thing at the moment i'm just waiting for traffic to grow.
If you put the time in 40 sites should easily get you £20 but on your calcs 40 website is 40 wks work and thats a lot. long term may be worth doing.
Difficult but i know if i had the dedication its a winner - depends really on what google do about affiliate sites possible make or break.