I'm joining some bounty campaigns and in my experience sometimes it is better to sell because you will expect the dumpers to sell their tokens and it will drastically change the token price even though they lock the token and increase the token price there s always someone who will dump their token but if their team and their vision and their ICO is reasonably good you should hold their tokens and wait for it to go to the moon.
For me everytime I received a new token with already have a value, I will sell half and I will hold the other half too because I am hoping that the price will rise again after many of dumpers sold their tokens. I just need to be more patient and controlling myself to sell all the tokens.