I have studied the graphs of many successful ICO's, they all share one common theme, that is everyone buys in during Pre-ICO/ICO and then dumps the coin within a couple of months of the ICO ending. The companies who are successfully building their projects and are regularly sharing their progress and engaging their community, these Altcoins go back up in value and usually surpass what the final ICO price was. So, my observation is you should buy low, sell high and buy back low again! That is if you are interested in taking a gamble on any of these Altcoins.
The biggest factor in a teams success seems to be their Crytographer and Product Manager - if you find a company with a good combination of these employees - there is a greater chance that the Altcoin will appreciate with a HODL strategy. Still, I don't see the harm in buy, sell, buy...just my opinion.