I think Jackie said it pretty good. I only had Tofu until Wednesday night. I was happy with just my one betta fish, I spoiled him and he was easy maintenance because it was just him. Then I ended up with two unexpected rescues (and now I definitely have no plans for anymore betta's!), so that's going to be two more fish to do water changes on, two more to medicate if they get sick, two more to maintain, ect.
I think going overboard is if you have a room full of betta's, and you spend literally hours doing water changes, and/or doing them pretty much every day of the week because you have so many.
HOWEVER, on that note, if they're well taken care of and you're happy, go for it! :)
For me personally, I live in a gulf state, so I worry about hurricane evacuations, and having too many fish. I have a ton of rescue dogs, but they're easy to board at a vet clinic or throw a leah on them and walk out the door. With betta's, it's a bit harder to prepare them for evacuation, finding a small carrying tank, making sure water doesn't spill, ect. And yes, I've evacuated with my betta's in the past. If we go, the dogs go, the turtle goes, and the betta goes too! :D