I do the same thing. I heat and dry, store in a vac seal bag with dessicant, a lot though, filling up the whole center of the spool. It seems to work fine this way with PETG. Haven’t tried with PA or PC but I have both PA and PC in the AMS also with copious amounts of dessicant and they print like the day I first dried them. RH in the AMS has been always under 20 usually 11-15%
I think the main thing you wanna make sure is the RH is 20% or under thereabouts in the sealed container you’re using.
I think the heating process drives off excess moisture and then keeping it that way via vacuum sealed bag with dessicant is working fine.
I do wonder why the filament manufacturer doesn’t heat and then store for sale. Most filament I buy is vacuum sealed with dessicant so it’s odd to have to heat it again. Maybe something to do with the heat tolerance of the spool they wind onto
Just Store your filaments with butt load of dry Desiccant in a large plastic bin with a lid will do the trick. Regen the filament in microwave when necessary. Lasts couple months depending on how many times the lid is removed. Achievable humidity is 25%.
a standard Home Depot bin works great. Poke a hole in bin and feed filament directly to printer for best results.