It is never a good thing to sell hastily.
It is never a good thing to sell below ICO price.
It is not also good to sell at exactly the ICO price.
There were times sold when i was not supposed to sell. Just because of the excitement of receiving tokens through bounty participation and perhaps through airdrop, i was eager to cash out.
Most of the times i did this, i always found out that i later ran at loss, not considering my effort and the time spent in promoting such project.
I could have also had 2x and sometimes 10x the ICO price, but impatience made me to loose the opportunity.

My last experience was on a token i received. Mentioning the name will be of no use, but for crypto enthusiasts to also learn from my mistake. Ever since then, i have learnt to hold and this has been profitable to me.
No matter how you got your token or coin, always try and be patient enough to hold until you are in profit.

That feeling is your internal buy signal!

If you are thinking of investing in ICO, it is always good . What we need to do is just value the project and relate it to the real time usage and the investor community behind the project. This will help you understand better and decide whether investing could yield profit or not.

my main intention working for bounty campaigns is to hold the coins for long-term and sell when the market is bullish

I am familiar with people who also participate in generosity companies. Some of them do not rush to sell received Tokines, others on the contrary, immediately after the issue of tokens the exchange is sold. My friend advised me to send them to EtherDelta. When receiving tokens, place orders for the sale of x2 - x10 (depending on the project) and just wait until they are purchased.
What do you do with the received tokens?