I'm not sure if you are in a high humidity/salty air environment, but body filler can cause you future corrosion problems underneath the filler material unless you are super careful, and even sometimes that isn't enough.
I work on helicopters in the gulf of Mexico area and have been involved with some major refurbishment projects and have seen areas of that had small, within limit dents or dings (usually from seat belts and shoulder harnesses around the doors) that were found during initial stripping.
We stripped the damaged area of paint and primer, inspected the dents for serviceability limits, chem treated the bare skin, primed, then body filled followed by finishing glaze and another primer coat then followed with main paint job color. Sometimes in as soon as a few months to a year we see shrinkage with the filler material that can lead to cracked topcoat paint and corrosion starting undetected behind the body filler that can get pretty bad and not even show up till the damage is done. It is time consuming,sometimes frustrating, very dirty and tiring job doing body work, so either practice a lot or find you a good shop that comes recommended.