If you decide to invest long-term, you should hold Bitcoin for the long-term, at least hold for the next 2 years. The current investment in altcoins is unreasonable because the altcoins rate is unstable, so invest and hold Bitcoin because in my view investing in BTC and hold is the safest way to earn profit later.
There is a simple rule: never invest in one cryptocurrency even when it is the best one - Bitcoin. Spread your money wisely. Pick several good altcoins like Cardano, Stellar, Ethereum Classic, and do not forget about BTC as well.