I have just checked the number of charging cycles completed on the three Mavic batteries,
for the first time ever.
33, 33 and 35 respectively.
They work perfectly up to now, but I am wondering when they might start to have faults.
Is there a way to check the number of controller battery charges, I expect it will be a similar number.
.
Sadly the controller battery isn’t intelligent so no stats are available.
As for the MP batteries, if they’re anything like the Inspire batteries (and they probably are) I’d say you could go several hundred charges before anything starts to fade.
If you’re worried, keep an eye on the individual cell values within GO4 
The controller battery doesn’t have a counter for charges. The aircraft batteries are much like any device, car, bike, lawnmower. If properly maintained they will last for ages, I’ve heard of many lasting hundreds of charges.
Thankfully there is a monitor built into the app to check the health of individual cells.
This is all about safety in the air. If you have a dodgy battery indicated don’t use it.