What did you learn in altcoins, those projects didn't paid bounty hunters even after successful. We can gather information by all unpaid bounties and with reasons why didn't paid. For us this is very hard when our good research is successful but admin cheated to bounty hunters. List why didn't paid, your experience and history about unpaid projects
You sure those were "successful" project and they didn't pay? Only those projects that fail or are scam projects are the ones that don't pay the bounty rewards. Are you sure those who didn't get paid actually didn't break any of their terms or rules when applying or while under the campaign? I have seen a lot of people complaining that they were scammed, but instead it turns out that the user himself was at fault.
Anyways, I would say those bounties are just waste of time. Avoid them and do something more productive.