If I have invested money in altcoins then I never hold them too long and sell whenever its giving me at least some profits as it can be bought again when price dumps and bitcoin is an long term investment for me so I will not sell till it achieves my desired price and till that time I will keep them safe in my wallet.
This is the correct way of trading altcoins in the cryptocurrency world - we should set a target amount of gain as our exit or sell even before we made our buy. This way, you will not get much of the emotion side of trading and instead just follow on the pre-planned trading.