You don't provide enough info to get much help.
Are you properly priming the new heads?
The wicking material inside a new/unused replacement head needs to be fully saturated before pressing the fire button even once.
Easiest to do a thorough job priming before installing head into base.
PG/VG ratio?
Could be too thick to wick as fast as you're
vaping, causing burning of the wicking material.
Are you vaping colored or sweet liquids?
4 replacement heads in a month could be normal using colored and especially sweet liquids which tend to clog wicking material & gunk coils rapidly.
Power range/setting being used?
Which replacement heads are you using?
Kangar offers a whole bunch of different ones.
Too high power will always cause burning.
Are all o rings/gaskets in place & undamaged/making a proper seal?
They can't wick properly if the tank isn't holding the negative pressure necessary to feed liquid to the head.
Under or over tightening head to base or tank to base will cause all sorts of issues.