How many miles before changing electric fuel pump 1996 Chevy pickup 1500?

dont change fuel pump due to miles. if it is working leave it alone, only needs replacing when it no longer works I had 150,000 miles on mine and it started showing signs of weakness, setting the check engine light on really hot days out here in the desert, yet running fine when temps were cool. Also started getting louder with the humming or buzzing sound. it's not miles.......it will eventually go otu but until then , save your money. The stock GM fuel pump goes for around $270.00 ............maybe a little less if you shop around.....