The time in the said marriage is the right of the husband and only he can forgo it. But it is permissible for the wife to make a condition in the contract that she acts on his behalf in this matter. She can then forgo the remaining time.
If there is an agreement between the competitors that each one of them pays an entry fee, in addition to a condition that the winner will receive a prize, then this agreement is prohibited. If the agreement was to pay a specific amount of money to the organizing committee for participating in the tournament, and the organizing committee has control over the collected monies in managing the game, without putting a condition that obligates the committee to give a prize to the winner(s), but the committee gives the prize as a gift without any obligation, then the agreement in this form is permissible.