We have never, ever locked away Halide from people who already purchased it. If you bought Halide 1.0 in 2017, you can still use it today, with all the features you bought, without paying another penny.
Personally, for the tiny amount I paid back in 2017 for the app, $59.99 one time now is cheap to me. That’s under $1/month over that time which is well worth it to me. If I got “locked out” if I stopped paying, then I’d feel different, but that isn’t the case so keep up the good work!