Generally, when you want to heat the beer is after fermentation has peaked. Higher temps means faster fermentation (obviously to a point), and fermentation generates heat (positive feedback loop), which is why you need to cool beer through the initial stages of fermentation). After peak though, the temperature drops and causes a positive feedback loop downwards. This means that your beer really crawls to the finish line. Your beer might be 90% done after 3 days, but then take a couple weeks for that last 10%.

Another benefit is if you are bottling the beer, you need to know how much sugar to add. Calculators ask for the beer temperature post fermentation to determine residual CO2. With a dropping temperature, it's hard to say what that point is, and if fermentation is just stalled, not complete, you could have residual fermentation sugar. Bumping the temperature up at the end solves both problems.

I also second adding a fan. No need for anything crazy, just something little to move the air. I used a old computer case fan wired to a random DC charger from the "miscellaneous chargers" bin at the thrift store: just make sure the voltage works with the fan.

Moisture can be an issue when you are keeping a fridge above the designed set temperature, but below ambient. I just keep a long sock filled with silica beads in mine. To recharge, I can just pop it in a low oven. They sell devices to do this (evadry is the brand name), but you might get literally 20x less silica for the convenience of a case and built in heating element.