I probably do it twice a year.

Big thing is to do something. Lots of people treat boots like garbage and then complain about their feet being sore and wet.

I replace mine every 4-5 years of daily wear by doing the following:

1.Get two pairs and a boot dryer. Rot kills boots faster than wear.

2. Saddle soap or whatever leather treatment you like when they get rough looking.

3. Get new insoles when they wear out.

4. If you work in industry, get oil resistant soles.