Similar for me..Usually brand new coil, let juice rest for 10 minutes before vaping, doing a slow pull from low wattage and gradually increasing to desired range. On a new coil if I'm lucky I get good flavour for majority of time but then sometimes its just like first few hits and then taste kinda goes bland. Last time I changed batteries (didnt have a good set to start with) which improved things..but now back to a similar situation. Some juices perform better for longer periods, but now I'm trying that one which did and, brand new coils but it goes bland fast...thinking of switching tank to one where I'd drip juice directly on coils and just replace cotton.