Personally I do believe HODL is a valid investing mind frame.
Currently I only hold three coins, bitcoin, x42 protocol (this will be my biggest winner I am quite sure) and stratis, which I will probably sell because I really hate the whole 'strax' idea.
If you believe in a project, no only in what they promise but what they have delivered, you should definitely hodl. At least imo.
I agree with you, holding crypto coins is still a valid investment strategy in my opinion. The coins I am holding for long term are Bitcoins and ETH at the moment, smaller holdings in other cryptos I would trade more quickly. The thing about constantly trading your coins is that you have to pay a lot of transaction cost and you need to keep finding new investments. I think it's very hard to be better than the market constantly, so I just prefer to hold my coins instead of being forced to rebuy at a higher price in the future.