I tend to clean and condition bags when I put them back into storage, like at the end of a season. I often just use Lexol cleaning and Lexol conditioning wipes for maintenance because they are easy and convenient and work on most bags (except patent leather that I just wipe down).
Vintage bags may occasionally need treatment with CPR or Black Rocks because they are older and may start to dry out and show scuffs and wear.
I spray bags with Apple Rain Garde when they are new (or new to me and rehabbed) and may refresh it periodically as the mood takes me! I am more likely to use it on bags that were expensive or are valuable IMO.
Great tips, thanks! Will need to add Black Rocks and Apple Rain Garde to my rehab tool kit!