The key to anything in game design or life in general is moderation. We each have our own pain to pleasure threshold. Most people fear the pain, alot of people indulge in the pleasure, a small amount of people indulge in the pain. Often pain or pleasure is in the eyes of the beholder. One man's milk & honey is another man's **** A static dose of either extreme desyntesizes you over time. Your tolerance or intolerance may rise or fall but we become desyntesized when exposed to an extreme nonetheless. Peaks and valleys make everything we do more exciting and rewarding.
Wait a second, if everything is done in moderation, everything will be lukewarm? Lukewarm is boring and uninspiring. It doesn't make me commit to anything, it doesn't make me commit to love or hate something. Therefore, I do not feel engaged or invested. There needs to be tastes of extremity to stoke the embers of the heart. Lukewarm is mainstream, it is played by many. But to achieve that mainstream, alot of the content gets watered down. Lukewarm will be received well but will rarely shock & awe.
Designing content should not be watered down. I'll use this example regarding timesinks. Alot of people play the lotto. Few win and most lose. The winners feel like the luckiest people on earth. The losers might or might not keep playing. But over time they lose faith, heart, they lose investment. If there were a way to make everyone a winner, no matter how long that took. Hell, if there were a foolproof, tangible way to get rich through hard work. EVERYONE would do it, they would feel invested & energised regardless of the time spent. There are no guarantees in the real world, but in a game anything is possible.
Just avoid the obvious timesinks. What is an obvious timesinks? Anything that has nothing to do with in game time cycles that causes one to wait or repeat something monotonously during advancement. That's my opinion anyways lol.