Should I increase my pumping time?

LO is almost 5 months. Since day 1 I've pumped once a day for 15 mins. Lately I've noticed that it takes longer to get to the hindmilk. I'm pumping more milk in general because baby is eating more, so there is more foremilk to pump. Should I increase my pumping time to make sure I'm getting all the hindmilk?