Assuming you're EV+, as a function of hands played, your ROR goes up until it a maximum, and then decreases. This is because at some point it's inevitable that your winnings will outweigh the swings you endure.
The maximum ROR that you will ever face is called your lifetime ROR. As you play more hands, your ROR actually goes down.
Oh, and yeah, ROR formulae are always based on 100% reinvestment into your bankroll. If you're not reinvesting 100% (for example, if you're living off of your bankroll), that can actually be treated as a net loss per hand (use the formula for replenishing bankroll but put in a negative replenishment number).