It depends on when I can avail them but if I invest, I'd do it before the halving happens. Just as bitcoin does, most of the altcoins are also going to move anyway after Bitcoin's reaction after the halving. If you have a better choice and you're able to buy at the same season then that's much better. You'll also DCA just as what everyone does with Bitcoin, if you are able to do so with altcoins and you should have done it before the halving for actual Bitcoin so you don't miss both ends.
In selecting alts, it is still best to invest on alts with actual use case as it will have reason to survive in the market.
Also, as much as possible, with active development and visibility from the dev team themselves.
Aside from bitcoin, there are truly worthwhile alts to look at. But should really do your own assessment on their existence.
You're absolutely right most of the altcoins is not worth to invest, that is why i don't look at altcoins because the risk in altcoin investment is very high, most of the altcoins pump so high due to hype unlike as you said earlier but all of a sudden they get dumped. altcoin investment is just the same as gambling because you can loss at anytime, I think the reason why most investors like investing in altcoins is just to make quick profit, well it depends on your personal decision for me I prefer to hold bitcoin for long term investment I don't care how much profit they make from altcoin investment.
That is one another difference between Bitcoin and other coins, as it gives investors to invest irrespective of the market conditions and any time you invest is a good time when it comes to Bitcoin so far your intentions is to hold for longer period of time, thou any involving in other coins should not do more than 10 percent size of their Bitcoin, yeah any one can whatever they like and should also be ready for the risk involvement too.
