This is one of my favorite strategies. I use USDT frequently, mostly for hodling when I'm not sure whether I'll be able to track the rates in the near future or not. So when I'm not going to keep an eye on the market I send some crypto to stable coins. The second option of using is the one you mentioned. I'm trying to grab added % to the innitial price by buying stable on the highs and selling on the lows.