i have two. i recently just made my second town, and i'm now trying to get all badges on it and all of dreamies in my second town, since my first town is already really completed in many ways, and i'm only just missing a few badges there
I'm amazed at the number of multiple towns people manage. It's hard enough for me to get one started with just one playable character. But I can see how I would be pressed to manage NL and NH towns at the same time once I get a hold of a switch.
I only have one 3DS, so I only have one town. If I ever can though, I wanna pick up a cheapo secondary 3DS off ebay and a second copy of the game someday to craft an experimental second town.
I have two and I still check on them even though I am focused on NH mostly these days. My first town I inherited from my bf so I am not mayor, but I got very attached to that island and made four player houses and did just about everything I could do (except PWP because those take forever to get pinged for, and I didn't play his mayor character that much which meant fewer chances). I then got my own version of the game and I made it a Star Trek themed town.
I lost my original copy of the game so I got a new copy around 2015 or so and that is my most used town. When the update came out I got another copy of the game not realizing I could just update the old one. I later gave the newest copy to my younger brother and still just have the one that I use