I've filled the two tanks I've used dozens of times. Sometimes I use a syringe to save wear on the cap, or if it's more convenient I just pop the cap off. They still work as good as the day I got them.
The tanks are only compatible with a tank atty because of their design. I believe the tank atty can be put on a 510 battery, though. They fit on my old blu batteries and my volcano passthough, and both of those can use 510 atties.
Different people recommend different lengths of time before a cleaning is necessary. From what I've read, most people wait a minimum of a week before cleaning. Some people prefer waiting two or more. I cleaned mine once I noticed a vast drop in vapor production. There are also many different ways people like to clean their atties, which aren't different than cleaning any other atty. Some just soak them in PGA, some people do a dry burn.
TPA flavors are from the Perfumer's Apprentice, lots of people like them.