For me Bitcoin has been my 100% portfolio and up to this point, I am glad that I choose that part even though Bitcoin price has undergone a lot of changes lately, my BTC vs $ balance has shown green and also red-negative movements which is a pointer to the activeness of bitcoin volatilities.
Knowing that Bitcoin is volatile in DCA pricing and also having a balanced market that shows not too much of a sign, e.g. 50% price movement within a few hours which is a sign of pump, or a drop in price significantly below 50% which is a sign of dumped.
Bitcoin has a cycle to help calculate its movement unlike those altcoins that have high centralization, subject to pump.
Generally, just like other people, I believe diversification is the best thing since it allows you to try other cryptocurrencies as well and you might even get some noticeable profits from some altcoins as we all know that altcoins are generally more volatile than Bitcoin because they have smaller prices, but, having and holding just Bitcoins isn't that bad.
If you talk about cycles and movement calculations, I honestly think that even if it has cycles, it is still not really easy to calculate its short-term movements and it can still move either way at any given time whether it is in a bull cycle or a bear cycle.