As stated in your owners manual (

idea: read thru it for more info), that is determined by operating conditions, offroading and similar dusty\dirty requiring more frequent service than, say, all hiway miles
Also, your service-repair sheet from the F37 event should detail what was done what was replaced - could have been just the reflash, so you'll need that sheet to get all your ducks in a row
I wouldn't settle for a flush, anyway - if you're having transmission problems, they should pull the pan, do an inspection of the oil and filters and see if anything is in the pan other than slight friction material from normal wear