I have never had an issue with desktop machines but I’ve tried using MacBooks as servers (with sleep disabled) and on both occasions they had failing hardware after less than a year (one had a battery expand and the other just stopped running one day and would not boot). It may be due to the hot summers here, but I know I’ll not be using them like this again.
I have had Mac mini’s run for years without ever sleeping though.
My mid 2015 MacBook Pro has been on Power continuously, except when I travel to work once in a while. I would say Prettymuch 24x7 and still going strong without any issues.
Keeping a MacBook cool is a real issue for me. I have a giant fan stand under mine but some things - such as Skype and Webex - cause the Mac’s fans to spin hard.
Nobody makes a chiller to put under a laptop - and maybe that’s because condensation might kill it. (I’m tempted to wrap freezer blocks in tea towels.)
I mention this since you mentioned hot conditions - shortening the life.