Personally I think your friend is talking out of his
If you're not having any problems, then leave well alone. The most important thing to do is to keep a REGULAR (as in weekly and ideally every couple of days) check on the water level in the coolant header tank.
As long as that remains stable i.e. no sudden topping up needed, then you're OK.
As SOON as you start loosing water, even a bit - STOP and find out why. Don't wait till tomorrow, the weekend, next week. You will end up cooking the engine that way!!