Holding a number of altcoins of course will give you many benefits for the future, but you must be more careful in holding some of your assets, choose a safe wallet to save your assets in the future.
Holding number of different coins will help any investor for not missing out any possible opportunities. It means diversification is always good because you will be covering all your known opportunities. But managing them effectively for securing them and watching them for making decision for selling kind of things are big hassles for any investor but by practice we can make it easy over the time.