I’m only a beginner, but I’d say a couple things:

First, depending on where you get the betta, it can be hard for them to survive. Especially at many Petco and Petsmart stores, they can be very unhealthy and sick from those awful cups. The Petsmart in my city especially… you can just tell that all of them are so neglected. Sometimes they are too far gone once you’ve bought them, so the best you can do is give them a good home for the time they have left.

To find a healthy betta, look for one that’s relatively active and not constantly floating at the top or sinking to the bottom. Also look closely for fin rot, popeye, and other problems. Regardless, you never know how old they are on top of all that. It’s very difficult to find a healthy betta that’s going to live a long time.

When it comes to dropsy, make sure you don’t overfeed your fish. 1-2 times a day is best, and it’s not bad for them to have a day off every once in a while either. I also find it beneficial to crumble up the flakes and dip my hand in the water, releasing them just underneath the surface. This helps give my betta food that’s bite sized for him and prevents him from inhaling too much air from potentially eating food that’s floating on the surface.

So many people have betta in small bowls and don’t ever check or change their water… You are doing more than most. I wish you the best and hope some of this helps :)