The striker is coming up to 30 years of age and realises the pressure grows on players once they hit that landmark.
Berbatov told BBC Sport: "I love it but football, you cannot do it forever. You hit 30, after that everybody says you are finished. But you have examples in our team - players like Ryan Giggs, Paul Scholes, Gary Neville - they are still going as strong as ever but everybody feels how the body feels and it's your decision but I will always think that you can quit as long as you are on top, that's the best time to quit.
"The thing is that the train as hard as everybody else, especially them (Giggs and Scholes). They are first on the pitch every day and still showing the passion for the game like small children - 'let's get everybody going as well' - so it's very nice to play with such good players."