ETH and XLM used to be my only favourite altcoins, but along the line, most especially when I noticed two other promising ones, which are Chainlink and Tezos, I now have four of them.
I can hold these four altcoins as long as I want because it believes in them.

I have always believed that if anyone wants to choose a particular coin, to be invested on, there should always be a strong reason behind it. This is why my choice is my choice, based on reasons. So, you should also do your own research to make the best choice for yourself.