No bleeding doesn't change the inhibitor to be weakened - not if you just remove gas and don't lose litres of water every time you do it.
Constant need to bleed is a sure sign of one thing - gas is getting into your system constantly. This is a bad thing and it shouldn't happen. It (nearly always) comes from one of two sources:
1) It isn't air at all but hydrogen gas - the product of corrosion inside the radiator because the inhibitor isn't concentrated enough
2) Air is getting in through the indirect tank - constant sucking of aerated water from the tank - then pushing it back up to the tank again.