If you want to make a long-term bet one of your options is to register your bet with the Long Now Foundation as a Long Bet. They have some rules, which are roughly:

• Both parties put up the same amount, at least $200/each.
• Long Bets effectively runs a donor-advised fund (DAF).
• When the bet concludes the winner chooses a charity to receive the money.
• The charity gets the initial stakes, plus half the investment income.

While people have all sorts of reasons why they might want to use Long Bets, one question is: how confident do you need to be for placing a long bet to result in more money going to your preferred charity than just putting the money in a DAF now?

Let's say I claim we'll have talking horses ten years from now, and you're skeptical. You consider betting $1000 against my $1000 via Long Bets. If you win you'll get your $1000 back, my $1000, and half the investment income which (figuring the stock market returns a nominal 7%) will be ~$967, for a total of ~$2967. On the other hand, if you had just put your $1000 in a DAF you'd have ~$1967. Is this a good deal?

Provided putting the money in a DAF for at least that long would otherwise be your best option, if you're 100% confident that (a) you'll win and (b) Long Bets will still be around, then it's a solid deal. You're up about 50%. On the other hand, the less confident you are the worse the deal looks:

(sheet you can copy and play with)

For example, at 60% confidence you're neutral at 6 years, and negative after that. At 75% you're down to neutral at 16 years. At 90%, 32 years. At 99%, 75 years. For an organization trying to promote long-term thinking, it's surprising they would choose a fee structure that penalizes long-term bets so heavily.