Just to give you guys some ideas about how lucrative this could be.
Say you work 45 Saturdays out of 52. Of those Saturdays you work a minimum of 4 hours (taking into account you worked 50ish M-friend) at 50.56/hr. By the end of the year you'd make 9100.00 more just from Saturdays. Say you've been here for 15years and plan on doing 30 and out. Doing 15 more years at 9100.00 an extra a year (no yearly raises calculated into this), you'd have $136,512.00. That would equal roughly two years of what someone who takes a few no pays every so often makes.
Now imagine you're ready to leave and took that 4hrs on Sat the whole time and dumped just that into a 401k for 15 years and earned 10% a year off it average. It would come out to be $318,042.54 over the 15 years. Now lets say your 55 at the time and can't pull from it till 60 and you're just living off your pension, the total at age 60 would be $512,210.69.
All that from 4hrs extra OT a week Saturday morning for 15 years working.