[stomachmonkey]

I have several pair in every room of the house. They are dirt cheap so buy them in 3 packs.

James is correct, different strengths for different uses.

Really they are not much more than a magnifying glass which as you know you adjust the distance depending on the situation.

As far as making your eyes lazy resulting in more deterioration, that's a wive's tale.

It's called Presbyopia. It's your lens becoming stiffer and has nothing to do with the eyes muscles.

Happens to everyone eventually. Fact of life you just have to deal with.