If the coin I am holding increase in value, I lock the profit I gain and convert it into a stable currency like usdt. When I piled up and reaches a desired amount, I convert to fiate and buy a bank investment
I believe in this thing that securing your profit is far more important thing to do than that of earning that profit. If you will not be able to utilize that profit at a better place, then there will be nothing good which you will be able to make us from that profit. It is better to invest that profit into any of the crypto currency again as this will increase the amount of money which are earning from that investment.
I think your last statement will not work 100% mate, how means suppose if you invest your profit in other altcoins and that coin price drops after you investing and it stable for a long time then you can't do anything you will lose your profit. better try to cash your profit instead of putting that money in other altcoins.