I think people are exaggerating a bit. nowadays players can stay in a good shape even in their mid thirties. remember Nedved's time at Juventus? he retired at the age of 36, and he always looked fit, and could have done a job for a couple more seasons. Solskajer? (can't really spell his name) him too.
Gerrard is world class in two positions, on a free role behind the striker(s) and as an attacking centre midfielder who runs the show (but needs a good partner).
he can play those two roles quite well, especially that now he can preserve some of his energy with all the competition on these positions.