Time travelling ruins the concept of the town growing in real-time and an incentive to play daily in my opinion, especially when the daily tasks such as fossil digging, money rock hitting, police station checking, villager chatting, item cataloguing and perhaps a few other things just take up a fair chunk of time. If bored, go to the island or do some online stuff.
Once time travelled just to scan a QR code whilst the shop was meant to be shut but that's about it, lol.
I do it when I want to do it. Does there need to be any other reason than that?
It's usually when I'm trying to get a villager in or out, or I'm trying to speed up a process that would otherwise take an ungodly long time (like getting access to the QR machine on secondary characters). Right now I'm planning my town's layout and I don't care to wait the time it takes for trees to grow just to see whether they'll look good the way I've planted them, so that's what's been going on with me + time traveling lately.
I have no issues with it. Some players are purists and will never do it, and that's fine too. I also routinely set the clock back a few hours so I can play during ingame daytime while it's night IRL, since I don't really like playing during ingame night (in a lot of games, not just this one).
I do TT, every time I play. I know a lot of people are scared to do it because of losing villagers, but I literally play each day out. I do all my chores, talk to villagers, stop or allow move outs if there are any pings, do favors, build up bells, everything. Then instead of actually waiting for the next day I TT to it. I'm literally playing right in the middle of a usual TTer and one who doesn't. Because of the pace I chose I usually go through 4 or 5 days per day I play. And if I ever go too long without playing then I will TT to the date last played so as to prevent anything from changing. And the only time I've ever reset was for if a villager I want to move doesn't, or if I accidentally pop a flower.
I usually TT by a few hours in the morning, since usually I don't have much time to play except when I'm on the train on my way to school at 6:30 AM. Every once in a while I'll TT for other stuff, too, though.
