There are a number of examples that say that sometimes in order to make a lot of money you just have to believe until the end and in ten years you will be a millionaire. There are as many opposite examples, which show that it is silly to keep some assets even in the short term. Hold or not depends on each specific project, if there is progress, the team works and develops the product - there are chances for growth, and if nothing happens, there is no usage and development - it is useless to keep such an asset if it is not gold or bitcoin)
I seen that recent Binance IEO project - Axie Infinity have dead ANN on bitcointalk from 2018, just imagine if you was one of the earliest investors/supporters - how did they managed to hold for all these years and only in late 2020 see that project launched IEO on Binance, these are really a long-term believers.