I've heard that Bitcoin will finish mining in 2140, which is certainly a long way off. There's still a chance for us to continue dca BTC, as there's a strong possibility that in the future we'll see a higher BTC price than today, as BTC is constantly being mined, and we'll eventually see the BTC supply dwindle. Currently, I know there's only a small amount of unmined BTC left, approximately 1,100,000. While the number currently mined is 19,900,000, there's still time to accumulate BTC.
However, I'd like to know if there will be BTC miners once the supply is fully mined, and will the fees for sending from wallets to exchanges be high? I also wonder if the price fluctuations will be similar to the current bearish and bullish market. Currently, BTC is widely traded, buying at a low price and selling at a high price. But will BTC trading be possible in the future, similar to daily trading? I think this is worth discussing...

Probably around 1.1 million BTC is yet to be mined which will probably be done by the middle of the next century. And after those are mined, will the minors disappear? No they won't. They will probably live off that transaction fees alone. There is an expectation of the fees getting higher because they will have to take better security measures. but everyday users likely pay low costs via layer‑2 tech like Lightning. Trading will not end as well. Also, volatility will remain as built-in feature, traded on markets, and used as a store of value. What about daily buying and selling? That will probably happen but far in the future. So yes, you can keep stacking sats, also enjoy trading, the miners are still going to be around even when subsidies end.