The selenium cell, if it is un-damaged, can last a very long time.

I have a Master II which gives reasonable readings, but have had a couple Westons that didn't work as well. In general I find they are fully good or totally bad (though the problem can be loose connections).

I think the Weston series of meters are "pretty well" designed, as far as protecting the selenium cell goes.

You might need to get in the habit of using Tungsten speed ratings that are lower than Daylight speed ratings. Sensitivity of selenium cell to near infra-red makes the needle jump higher under Tungsten than it should.

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By the way 1 stop higher reading of 18% gray card seems perfectly reasonable.

I accidentally did an 18% gray card exposure test, so here is the graph...

Basically the lowest diamond on the lower-left of the curve is 2 1/3 stop below 18%. (18% is the middle of the cluster of diamonds mid-curve). Imagine that lowest diamond is about Zone III. Really would have rather placed Zone II down that far on the curve. So one stop more would have been a better exposure.