Dells aren't designed to last longer than warranty period, but depending on the class of the machine the warranty may be as long as 7 years ( on Servers ).

top DIY market motherboards and power supplies come with 12 year warranties now, but i like to replace computers every 5 years anyway and Dell does offer 5 year warranty on the class of machines i buy from them ( workstations ) and workstation warranty is next business day on-site. you don't lift a finger - the tech comes to you.

i actually feel oppressed by the fact that my 12 year old DIY PC still works, because i don't use it but i'm also too cheap to just throw it out.

only downsides to old machines failing is it's harder to get your data but you should back up your data anyway.

i once heard a saying " data that isn't backed up doesn't exist " and i agree with that. it's similar to " you only own what you can defend " and so on.

your personal time is better spent backing up your data than trying to build an indestructible computer.