When is it time to buy new hardware?

Hi there,

We are running mostly HP LH3 server raid L 5
with twin processors… we recently had a problem with one of the servers, which luckly I had an extra main board on site to fix the problem. My question is this the server are now over 3 years old, should I be thinking about replacing the servers next year? the warranty has run out nd I need to renew… what is the general rule of thumb?

Should I replace after 3 years / 4 years / 5 years even 6?

Thanks

Toby…