Bleed my brakes again?

I'm working on a friend's car and I've already bleed the brake system. The system suddenly had a decent amount of pressure and I found a bad brake cylinder on one of the rear drums, so I replaced that and bleed that side. Then I split a front brake line, and just finished replacing and bleeding that side. Should I bleed the entire system again? The brakes don't seem to have any guts until the very end of pedal travel, but if I pump them, I can feel surges of braking power near the top of the pedal's travel. Whats up?

I kept bleeding and bleeding and finally I found a section of one of the rears that pushed nothing but air for 3-4 pumps of the brake pedal. (And here I thought I had flushed the whole system) I guess its not a huge surprise that the brakes feel like new again! **** HINT FOR NEWBS **** If you are trying to bleed brakes, try to bleed each wheel 2 - 3 times. I didn't find the "real" air in the lines until the third try.