Can't you set IP reservations on routers these days, so you can always leave the computers set using DHCP, and let the router sort out giving the same IP to the same machine each time?

At least you don't have to touch the PCs then should you replace the router

Plus in the case you do have hundreds of machines, you still have a central record to keep track which machine permanently gets which address whilst leaving them all on defaults instead of manually configuring them all
I just do DHCP reservations on my linux router (from 192.168.0.2-129) for all the home machines, and use 130-189 for any "unrecognised" or guest machines.