I have a selenium hand held light meter, Sekonic L-158. Years ago I was told to keep it in the case when not in use that was included with it as constant exposure to light with the selenium cell gradually degrades it resulting in inaccurate readings.
Information to help:
Truth be known, I have thought that it is like pushing water uphill to get everything perfect or near perfect with photography exposure. With film there are numerous variables, from the light meter, to the camera shutter to the batch of film used, to the many variables in the darkroom.
With digital, I find not as many variables but still quite a few.
Wih negative film I leaned to slightly over exposure, with slide slightly under exposure.
Digital I treated the same as slide film. I use the histogram and when I see the right wall getting touched I know I’m getting into the danger zone of over exposure. I also capture only using RAW as that gives me a file with more information to correct when I need to.
One of the most serious sins, at least it is to me, is when I see photographs that don’t have the proper balance of light with the foreground, middle and background. Blown out or very dark sections of a photograph are a no-no for me. When I was in business, during client interviews, I would show them this and, usually, they didn’t notice this until I pointed it out to them. It made my job easier, getting them to sign a contract with me, as so much of this is around, especially today, as a reliance with so-called automatic cameras.