I for the past year have run the heuristics on the highest settings. I've noticed two things:
A. It doesn't really seem to detect anything more than it did
B. I've not seen a false alert yet.
I also run a script that downloads rapid release defs when I "see signs" of increased activity or "risk out there".
I was running it 24/7, but decided to scale back and run it only sometimes
As far as the rapid release defs, I do believe they have saved a computer or two here over the last several months.
It's risky, but so is under protection. Computing on the Internet today is in itself a calculated risk..............