Here's a twist on prospect theory.

I installed solar panels, which were pretty expensive, but pay back as they generate electricity.

The common question was "How long will it take to earn your investment back?" I understand why they're asking. The investment is illiquid, even more than a long-term bank deposit. But if wanted to get my money "back," I'd keep it in my checking account. The question comes from a tendency to privilege a bird in the hand over those that are still in the bush.

The important point they should ask about is my probability-adjusted return on investment.

If the panels have a total breakdown before I get my investment back, that's bad, but it's just a negative RoI, no worse than losing money to inflation or to a down stock market.

If I get my money back, and then the panels break down right away, I won't say "at least I got my money back," I'll say "I wish my RoI had been greater." If I get my investment back, but it takes far longer than I expected, I won't say "at least I got it back." I'd say "too bad that my annualized RoI is near zero; at least it's not negative."

And if my RoI is super-duper, and I get my money back quick, I won't say "hurrah, I got my money back," I'll say "hurrah, I'm getting better RoI than any other investment I can make today," which is actually what I'll say even before I get my investment back. And then I'll keep smiling so long as the panels keep laying the golden eggs.