Photomultiplier life time

[Zagros]

Hello guys.
I recently integrated my meteo station with a pulse counter with a 30x70mm BGO crystal coupled to 50mm Hamamatsu r1306
The intention is to monitoring the background 24h/day.
Now my question is
How much lifespan I have to expect from the photomultiplier?
The divider has,high resistance (80mohm) so the current in the pmt is low but it is counting 200cps of background al the time.
Opinions?
Thank you

[Madmax]

In this case it will work tens of years, if there is no leakages in PMT.