It is indeed safe but it should also be considered the composition in managing the portfolio, you should have more bitcoin than altcoin to avoid the risk of storing money in altcoin, so you will get a much greater chance, such as 20% in altcoin and 80% in Bitcoin, it will be very healthy for the development of your investment towards the future, especially if you invest in Altcoin which still has a centralized system, you must be careful even though coin is quite famous and hype in the market.
This is true, having a portfolio that is diversified is an important situation, because it gives you a great return when you have a good portfolio and not only it helps with a lot of downs, but it also helps you with further profiting as well, very important situation to be in. I believe the best thing to do in this case is to have a portfolio as deep as you can while keeping bitcoin as your number one.
A lot of people say the highest you should have for a single asset is 20% at most, and I agree with them, I have more than that, bitcoin is half of my portfolio but I can see 20% being a lot better. This way, you could have 20% bitcoin, 20% ethereum, and then the other 60% could be 5% each for 12 different tokens and coins as well. This would give you a much better situation, and at the very very worst case, bitcoin and ethereum will go up twice and then some in the future, so you will recover everything even if those 12 coins and tokens go to zero.