How often do you have to calibrate the sensors?

just a simple question but yet substantial.
How often do the sensors need to be calibrated?
After each flight?
After battery change?
Every so often after xxx days?

Is there a rule for that?
I have the apm 2.5 module…

Probably going to be told it should be done more often, but, I calibrated the Pixhawk on my quad when I installed 3.2.1 and haven’t done it since.
That was 11th February 2015 and has flown fine since in manual control (Primarily PosHold) and a few auto missions too.

unless release notes for a new firmware tell you to recalibrate something after upgrade, there is no need/point in doing so.

Thank you very much for your information.
The reason asking was that I have flown the quad about 6 month ago and this time it tilted extremely during take off. Last time it did not behave like that.