Although today there are many online tools for help documentation writing, many users still prefer desktop software due to various reasons: from security and reliability, to better performance and better UX.
In the past, we offered only perpetual license with free upgrades within a major version (e.g. 5.1, 5.2, ... etc) Since July 2021, we offer 1-year subscription licenses. So, about a half of year is still required to see how the new licensing model works.
The profit is enough to support a small and agile team though our niche got a bloody ocean and we have to run faster and faster only to stay in the same place.
From my experience, desktop software still works well in vertical and professional niches. In B2C or mass market, mobile and web tread on.