you are right, some of the coins from the bounty did not have a great development, and it makes better we sell in the beginning. but for a great project, we could see growth in 1 year and some of these coins have a very successful ride more than the price of the ICO they.
unfortunatelly 7/10 bounty campaign i participated are failed and ended with scam, i hold many token from few project and trying to keep hold them in my wallet and not sold early, but i got sadly ended, nothing any development, innovation and news from dev.
My advice for you, everytime you received the tokens from bounty, go directly sell the tokens on the exchange.
Because if you don't sell your tokens, the price will fall fast because many bounty hunters will sell their tokens too. Imagine if all bounty hunters sell their tokens in the same time.