An OM10 goes into a low battery drain condition after 90 seconds unless it is in a tight fitting g bag, and the first pressure tripped repeatedly, if you carry a OM1 all day with cap off and switched on in good light it uses battery all day.
Originally Posted by McErland
You don't need to turn an OM2 on if you know the shutter speed is going to be more than 1/30. It does an OTF and 1st blind pattern exposure reading even when switched off doing an ok exposure from 1/1000 to1/30.
I never turned my OM2 on or replaced batteries.
Don't think you need to turn on an OM10 either just hit the shutter for good exposure.