Which Dell desktops are you using, OP? I have been 99% DELL my whole career. I remember some capacitor problems on Optiplex mobos like over 10 years ago. At my current place, I have had Optiplex 380, 390, 3020 and now 7040 SFF. I have only had like 2 or 3 in 5+ years have any issue within 4 years of their in-service date.
As far as laptops go, I am still a dedicated Lenovo ThinkPad T and X series fan. Most of the problems are software related. Only occasionally do these not last a full 3 years for my remote sales personnel, who travel domestically and internationally all the time. Once they hit that mark, they are in line for an upgrade and the decent units that still have life left in them are re-purposed in-house for a variety of low-level workloads.