Is the SMD Uno more fragile than the DIP version? I have 5 UNO's. I've had 3 DIP versions for a couple years. They all still work fine. I recently bought 2 SMD versions. Both worked for a short time. Now the IDE can't find the COM port for either of them.
From my own usage there is no durability difference.
Have both version here and some run 24/7 for months at a time until I change the sketch.
People report failures of both types and quite often it is due to abusing the poor thing in some way.
Some boards have regulator issues but those of us who appreciate thier boards run input voltages less than the recommended or max which of itself seems to prolong the life as the regulators have less work to do.
The COM port disappearing is a failure of the 16u2 used as the serial adapter on official unos. It is very easy to damage from abuse of the power rails, even some things that don't seem obviously wrong. It's unrelated to the package that the '328p is in.
If any of the boards are clones that use a CH340G or CP2102 for the serial adapter, those are more resiliant to this kind of damage.
Thanks for your help. With the information provided I reinstalled the CH340G driver, and all is well.