The decision to hold or sell a token gotten from bounty campaign depends on how good the project is.
If it is a very good project, it is better to hold the token but if it isn't that good, it is better to sell off and buy other tokens.
Some tokens simply need to be sold at the first opportunity, but some need to be kept as long as possible, everything really depends on the project. You can also use the tactics of partial sale of tokens, this will help reduce the effect of a sharp price change.