I have been building my own computers for the last 25 year upgrading every 3-4 years.
In that time I have never had any issue with degradation.
Most my upgrades have been because windows and the latest games advances have just made my CPU graphics card obsolete and just not up to the task.
The rest have been quality of life upgrades like SSD(OMG what an upgrade), better monitor, better keyboard.
Generally your CPU will be obsolete before you have degradation issues.
Someone overclocking and heavily stressing their CPU is unlikely to suffer any degradation within the 3 year warranty otherwise AMD would lose too much money.
Running cooler is still better since boost clocks are limited by temperature.
I remember the good old days when windows took over a minute to boot up and McAfee would lock my computer up for half an hour during a gaming session