use new psu in old build?

Hi everyone :-) I've got a few bits to go towards a new build, but it'll be a while until I've saved enough to complete it. Is it worth putting the new PSU into my current old build for now or just waiting til I've got all new bits and use it then so everything is fresh and new together?

Cheers

If your PSU is working fine and of sufficient quality, you don't need to change it for the sake of :)