A good 7 years ago, I bought a Shuttle SX38P2 Pro which has been running pretty much 24/7 ever since. Recently the PSU fan has been struggling, but I can’t complain for the time it’s been in use. Over those 7ish years I’ve suffered a single drive failure.
# smartctl -a /dev/ada0 | grep Power_On_Hours
9 Power_On_Hours 0x0032 081 081 000 Old_age Always - 13972
# smartctl -a /dev/ada1 | grep Power_On_Hours
9 Power_On_Hours 0x0032 015 015 000 Old_age Always - 62738
As the fan was struggling, I contacted Shuttle to ask about replacements but received no reply. That was disappointing, but I guess understandable as the model has been discontinued (I didn’t think the cooling was model-specific though).