I doubt CPU usage and heat has anything to do with "battery swelling".
Instead, an important question:
Do you normally keep the MBP "on the charger" all the time, or even "most of the time"?
If so, that's what's probably "doing in" the battery.
You should take it OFF CHARGE at least every 3rd day, and let it run down to about 40%, then re-connect to the charger.
At night, whether you sleep the MPB or shut it down, you should also disconnect the charger, or unplug the charger from the wall.
BTW, I would pay the $199 to Apple for a battery replacement.
When you think about it, it's a bargain -- includes battery, labor, and a short warranty on the replacement as well.
Rather than creating a new thread, I just received my mid 2015 Macbook Pro back from Apple Repair, excellent job, new top case, keyboard, I think it included a new trackpad, new battery, looks and runs as if it is brand new, for $199 plus tax.
I started to notice the lid not closing fully about four years after purchasing it, waited two years until the first physical signs of the case swelling began. In those six years I had a very low battery cycle count, because I typically put the Macbook Pro to sleep, unplugged the charger, next day when I took it out of sleep, battery was usually around 96 percent, I would immediately plug it in and use it throughout the day on plugged in power, then repeat at night, sleep with plug removed.
I really don't want to keep it on battery during the day, every single day, because I get about six or seven hours before the battery reaches 30 percent, I really don't want to plug it in twice a day to refresh the charge, I am repeating what you wrote, the every 3rd day recommendation, is that based on anything you have read? I really want to get at least two years out of this new battery before any battery inflation issues start up again.
Obviously nothing is set in stone, but if I can get away with only operating on battery every 3rd day, it would make things easier.
Thanks for your time and help.