I personally think that the 24 hour limit for each problem is a bit harsh. If you don't submit the solution for a problem in those 24 hours you are out of the contest and also you don't receive any leetcoins for that problem.

I do the problems because I find them interesting and fun and I don't care for the rewards but knowing that I receive some leetcoins and there is also a small prize at the end adds a bit of artificial motivation to all of this.

There are days when I'm exhausted after work, it is late, and focusing on a difficult problem won't get me anywhere, while doing the problem the next day, with a fresh mind, makes a big difference.

We should be allowed to submit the problems even after the 24hour mark and still be in the contest and get a few leetcoins. Give us less leetcoins if we don't complete it in the first day but give us something. Even if it is just in a week span for example, if you don't solve the problems before the week of problems ends then it can be game over.

I don't think that the majority of people are participating in those monthly challenges because of the rewards but instead because it motivates you to keep solving problems. If I miss 1 or 2 days then that motivation to continue might suffer. I have friends who droppped the challenges completely after they missed 1 day.