Do you keep holding it hoping that the price will finally come up since it seems you can't actually trade it with it current value.
As for Altcoins, we don't know what crazy things will happen to them. Consider them currently as meme coins, with low value, but at some point their price can grow greatly. I have participated in many Altcoin signature campaigns, and many of them grew very large when I forgot about them for a long time. Additionally, we are in the early stages of the bullrun cycle, so I think there will be many surprises as well as outstanding growth of Altcoins in the near future. So, you don't have to rush to sell them at this time. If you have more time, research the projects you are participating in to strengthen your confidence to hold it in the long term.
Will the altcoin become valueless after the campaign is over or could still gain value after some years.
The possibility of certain Altcoins becoming worthless is not a little, even a lot. Therefore, taking the time to learn more about the project you are participating in is also a way for you to predict its future. There are many factors you can rely on to evaluate, such as what is their roadmap in the near future? Is it feasible given the current market scenario? Evaluate the project team's activity level on social networking platforms such as Telegram, Twitter, Discord to have your own conclusions, because no one can answer better than you find out for yourself.