How long do you typically stick with a game before you begin to lose interest or need to take a break and play/do something else with your free time?

Looking at the playtime of games I've 'taken a break' from and swore I would get back to, it seems to usually be around 20-30 hours for me. Hbu? 

Depends on the game really.

My first playthrough of Xenoblade Chronicles took me 90 hours and I never lost interest, same for when I played through BOTW in around 100 hours.

Those are especially great games though; in a 7-8/10 game I tend to need a break after about 15 hours to play something else.

If I buy a new game and it doesn't grab my interest within about an hour, I tend to shelve it permanently.

Otherwise I prefer games I can play in 20-30 minute stints out of convenience.

Considerably shorter than it used to be.

Back in the day before I was in a relationship and had kids I could game for 40+ hours straight. These days anything more then 2 hours is difficult.

I give games that people say are good around 20 hours before I put it down if I do not like it.
Games that I just try out get an hour if I do not like it.
Games I like I can play constantly for decades.

I don't buy games that don't grab me enough to finish them. If I somehow manage to buy a dud by mistake, it becomes evident very quickly and then I just drop it.
If I really enjoy a game, I'll be sad that it ends even after hundreds of hours.

Generally I don't boot up the same game twice in a row, with some exceptions if I had to cut a session short but wanted to finish something first before switching games.

But that doesn't mean I never come back to those games. Oxygen Not Included and Hearts of Iron IV both have over 1000 hours on Steam for instance, and I have 8 more games on Steam with 100+ hours played. And all this ignores GOG (and everything pre-Steam) where I also have several games played for 100+ hours.

around 1-2 hours. If it doesn't grab me by then, I will usually shelve it for years.

very different from game to game but what I can say is for single gaming sessions, I often played a game 6-12 hours without a break on a single day until I was like 30 and now with 40+ I can't play more than maximum 3 hours until I lose interest for that day even if I love the game.