I have been wating to score a X7-M to upgrade my Nitecore TM28.
The TM28 suffers that same issue. The "smart standby" switch on these high powered lights actually draw quite a bit of current from the batteries, enough so to drain the 4*18650's in a week or less. Not an issue with regular clicky switches that do not have a standby mode and cut power entirely.
My solution on the TM28 is to just "crack" the battery pack by unscrewing it enough so the light does not power on with the button, creating a sort of manual lock-out, but the TM28 pack unscrews in the middle of the light where the the X7-M has the tail that unscrews so I am not sure if this would be a viable or convenient solution for the X7-M, beyond adding a step of tightening the battery pack before switching on, but a step that will allow the batteries to be ready for action months down the road.
Beyond the battery drain of the button, I was not comfortable leaving the TM28 in a standby mode since if accidentally turned on in its sheath with the power and heat it puts out, the potential is there (albeit slim) to start a fire! Probably not so much of an issue with the X7-M since it has a proximity sensor that will step down the output when an object is right in front of it but something to be aware of with the power it has!
Good luck and let us know if this works for you.