I think it depend on the project itself, if the project you are hodling is not showing any potentials, it is very wise to sell while you can because not all alts deserve to be hold for a long period of time, you have to see potentials or activeness on the part of the team to hodl.
Recent projects provide a very long roadmap that will always whet investors hope in the development. There are also more partnerships at different stages that could generate volume with the use case. New projects know they can't afford to sit down and just see price pump like in the past, while they wait for bullrun they will keep the project up even if the price is dumping. This could only give hope to any of this project when new investors approach soon
Ofcourse, having a working product is the key to experience longevity in the crypto world nowadays, gone where the days when project were base on only hype, pump and dump, now things are getting more serious, it is in the best interest of the project team to work towards having a real product to support the project otherwise it won't last long.