Firstly do folks leave it on or turn off the power when not in use?
Do you mean a MPS-2 Power Supply?
I don't own a BP 26 powered by a MPS-2, but a BP 25.
I can only tell what I do with mine, which is a BP PSR Rev 3.2: sometimes I leave it On, and sometimes Off.
During summer, which is rather hot where I live, I switch it Off.
Most of the time, I tend to switch it Off but turn it On 10 to 20 minutes before I turn my amp On.
Sometimes, I Mute it before turning the amp On.
Never noticed a substantial difference.
But the MPS-2 Power Supply is a much more sophisticated unit.
If I had one, I think I'd prefer to switch it Off when not in use.
Fernando.