Honestly, in all the years I'm playing this game, I never had one town where I could
say it was "completely complete". There was always at least onething in my town
which wasn't finished and where I worked all the time on it, whenever it was the
placement of trees, to re-build the other character's houses, redesigning my mayor's
house etc. Basically, I always had a town which wasn't complete, it was kinda complete
in a way where I was happy about it, but could have been better, to say it that way.
And I'm not going to start talking about "completely complete" the whole game. That's
something I never managed to do in any Animal Crossing game I played, lol.
Anyway, I guess it's the best to not rush at all, to take the time to complete your town
until you think "yep, it's done". Depending what kind of theme you want to have in your
town, what villagers, characters and all that, it can take some time. To say it that way,
it varies from player to player. But yeah, like I said, take your time, the best thing what
to do in my opinion.