If what you've got are older N frame Smiths and a modern 629 and an SBH, is extensive dry firing to be avoided or not, and why?

And how much dry firing is too much?

I suspect the answer is avoid it, but I'm not for sure. It does seem otherwise to be a good practice technique for working on your trigger pull and seeing if the sights are still on the point of aim after trigger pull.

I have dry fired all my handguns quite a lot with no ill effects. The only one I did not dry fire was an old Colt single action with the firing pin on the hammer.

Had an instructor tell me once, if you are afraid something is going to break when dry firing, what's going to happen when you fire it?

If you dry fire to much and you wear out or break something, get it fixed.

About the only handgun that you should avoid dry firing is a rimfire cartridge. It causes the firing pin or striker to damage the chamber's rim. Other than that, I have dry fired all of my S & W's for years. Makes good practice for when I was shooting competition.

You also should not dry fire Encores or Contenders.

Purchase a factory snap cap or pop the primer out on a empty case and cut off the eraser from a new pencil and cut it to fit in place of the primer.