QQQ Only Has to Drop Back to May 2019 Levels for You to Lose Everything
TQQQ seems like a very profitable opportunity right now. I would invest whatever I could survive losing in it, too. However, there is a non-zero possibility that it could go to 0. The way leveraged ETFs work is a little more complicated, but in my simplified understanding, if the Nasdaq drops 34%, TQQQ drops 3 x 34% = 102%. (In reality, it never goes to 0 for some reason. It just gets so small it's effectively like 0. )
TQQQ has only existed for 10 years and they've been nearly the best 10 years in the history of the market. So the charts aren't going to show any good examples of what can happen in cases like the year 2000. One might want to keep the very unlikely downsides in mind when figuring out how much to allocate to TQQQ.