>1) Could overheating be the cause?
Yes, it could.
Is the airflow obstructed?
Dirty filter?
Fan(s) not working?
Hot air exhaust restricted?
Does it go off repeatedly, or only once per day?
>2) How one can decide when the laser should be replaced?
I've never seen one go like yours; usually the current increases slowly
during the life of the tube, then one day it refuses to work.(ever again)
>Any other suggestions?
What does BD suggest?
What does the laser manufacturer suggest?
If a component is failing due to heat, it is likely to be some small
electronic bit rather than the laser tube.
Cheers, Joseph.
-- Joseph Webster Flow Cytometry Facility Centenary Institute