Here are some formula to calculate your earnings :
Calculating profits with a referral
per month
[ 0.005 X AverageClick X 30 ] - 0.250 = profit
per day
[ 0.005 X AverageClick ] - [ 1 (divide) 120 ] = profit
Calculating when u should not recycle your referrral
assume rented referral's average click = 2
($0.005 X 2) = 0.01
recycle cost = 0.8
8 (divide) 1 = 8 days