I’ve been replenishing my paper developer for about 3 months now. I’ve been working with 2 liters (printing 4x5/5x7 prints) and I just add fresh developer to top it at 2 liters, every second session, as I lose about 200ml per session. I’ll go on indefinitely with this replenishment regime. It not only makes me save quite a bit of developer but the results are excellent.
Granted, for this to work, you must be printig at least every week.
As with D76, a seasoned dektol is the way to go. I’ve been adding dektol, ilford multigrade and kodak polymax-T to the mix.
I cannot say what exactly is special about it other than saving at least 50% of developer, and the results are excellent.