infallible
1 True Mayor of Westeros
TTing is safe in moderation. 
when i TT, i usually TT a day at a time. to check the shops, talk to villagers, check the stalk market, etc. i probably wouldn't suggest tting more than a few weeks.
when i had wild world i did that money trick, where you would put a lot of money in the bank, time travel 99+ years into the future, and tt back and the interest over that many years would equal an extreme amount of money. however, that was a big mistake, because i came back to a town full of weeds, many new villagers, and a big, ugly raffelesia plant in the middle of my town. D:
so i would just suggest to take your time travelling slowly! a day or two at a time, make sure you talk to the villagers you want to keep every time you travel.
when i TT, i usually TT a day at a time. to check the shops, talk to villagers, check the stalk market, etc. i probably wouldn't suggest tting more than a few weeks.
when i had wild world i did that money trick, where you would put a lot of money in the bank, time travel 99+ years into the future, and tt back and the interest over that many years would equal an extreme amount of money. however, that was a big mistake, because i came back to a town full of weeds, many new villagers, and a big, ugly raffelesia plant in the middle of my town. D:
so i would just suggest to take your time travelling slowly! a day or two at a time, make sure you talk to the villagers you want to keep every time you travel.