I just completed my first year of retirement. Excluding spending on the rental property, I budgeted $120k/year of spending. I actually spent $129k. However, that included ~$28k on deferred maintenance of which $6k was budgeted. We knew that there was deferred maintenance to be completed. Also there was no vacation (we went on vacation in April last year and will go on vacation in June this year so no vacation in the year) which we budgeted $12k.
So excluding vacation and maintenance we spent $101k and budgeted $102k. I don't control the spending, I just track it after the fact (It is my nature to be cheap).
To set the budget I took the spending we did the year before we retired, estimated what was "work expenses" and subtracted those out. I still have kids in school so there hasn't been much "fun" spending.