I would split the total: 40% BTC, 40% ETH and 20% XMR. Then you can use some ETH or BTC to buy low caps coins or ICOs
That is a reasonable choice, I also hold much btc and eth than any other coins since I treat them as a long term investment, I like to convert between eth and btc, I find it is very profitable, the ratio is much stable than the price, and I do not worry about losing any coins.
Yes, bitcoin and ethereum is a good choice for long-term investments in crypto currency. These coins are unlikely to disappear in the near future, these projects have come to the world of crypto currencies seriously and for a long time. Yes, the current market drop has hit hard on these and other coins, but it shows that at the moment prices have become very attractive.
Most coins WILL disappear from the markets. They will either get delisted or not work anymore. Bitcoin and Ethereum are the top choices.