He's already surpassed a previously optimistic prediction. If you'd asked me 3 years ago, based largely on the fact he relied a lot on his pace, I'd have said probably 2/3 years.
Well here we are with him now.
I actually think he can go for another 2 years potentially. The fact he started late, the fact he's a bit less reliant on his pace than he was, the fact we use him pretty economically now (it's not uncommon that he'll touch the ball about 9 times but score), I think we might've prolonged him for a while yet. He'll always have the finishing and the intelligence and his passing and whatnot has improved no end in the last 2/3 years. I think we will buy another striker this summer but he will still be the main man for a while, we'll eventually phase him out gradually but I think we'll still get goals from him for a while yet personally. I could be totally wrong, but it's how it feels to me. Rodgers has handled him the best of any of our managers I would say.
Puel tried to phase him out 2/3 years ago. That looks a silly move in hindsight.