What are signs of a weak fuel pump?

I don't think there is any warning of a failing fuel pump. Some people will say a loud whine is an indication, but I replaced my fuel pump at 38,000 miles and my new one whinned very loud from day 1. It is still running strong at 90,000 and still whinnes loud.sometimes the pitch of the whine will change, but i can't tell u why.