It doesn't feel right to have to use 0/0/0 auto challenge spam to farm prestige counts, and also it means you have to keep the tab focused or else when you come back to it it lags like crazy.
The P/T/R counts gained from a prestige should scale with time since the last prestige of that type, and compound with the already existing multipliers. Maybe even new GQ or oct upgrades to increase that scaling to make all levels of the P/T/R achievements completeable.