Bitcoin : because it is no.1
Ethereum: this crypto is down these days, but I have got a news that ethereum 2.0 will roll out this year. So, I hope that this crypto currency price will go up.
Binance: because of stability
I understood why you chose BTC and ETH. What about BNB? I did not get your point about stability. Also, BNB is exchange based coin. Even if they add extra features to ıt, BNB will not be whit without Binance. If you consider these investments as long term investments, you can choose more reliable ones. Have you considered LTC or DASH? There was a very good increase in both in the last increase and this was an indication of mysterious potential.
I think Binance is really have a stable market. Yeah youre right, Bnb would not be worth it without Binance but they are keeping tabs with a lots of progress and I think OP recognize their dominance compared to its competitor which I believe is also a good option for long term since Binance is used by a lot of traders. Not a bad choice IMO.