Best software for 5X+ BATTERY ISSUES?

May also be worth looking at what CIQ addon's you have. Watchfaces etc? As a quick thought, are you using any third party, data heavy watchfaces?

Bluetooth always off

Watchface is Actiface with same setup I've used from the start and even on last Fenix 5X(non plus version) I had.

and no other strange installs, even removed music. 

Biggest problem is that my  battery drains AFTER a GPS activity (Run Bike etc).

I use a Garmin Ant+ HRM for all my activity's.

Link to old Firmware versions??

Similar to me then (HRM, no music) though I do swap between stock WF and Infocal.

http://gpsinformation.net/allory/garfeat3.htm

Any use?

Which device do you have and what's your typical drain? 

Did a 2hour gym activity yesterday. So Hrm only no gps.

And - 20.8% in last 24 hour which is ridiculous! 

I have a 5x+

Batery widget tends to suggest I have less than 0.4% per hour at the moment = 9.6% per day. But I did do a 2 hour run yesterday.

I go out 4 days a week, 3 of them 2 hor run's, the weekend one between 3-5 hours. I use a HRM, and tend to charge my watch at around 20% ... I'd say charge every 8 days or so? I don't really monitor that side too closely as I do seem to be getting what is said. For my long runs with GPS and HRM I tend to get around 3.5% per hour usage so thats what 25-30 hours GPS tracking?

Best of luck!