From my point of view the "jetbrains" licence model is one of the best:
- You can purchase their software with a single annual fee or 12 monthly fees
- If you purchase with an annual fee you can use the last updated purchased version forever.
Also, if you pay for 12 month continuously you have the same advantages
- If you purchase the same software for 2 sequential years you will receive an automatic discount and at the end of the third year you will obtain a fixed discounted price (if I remember correctly around 20% forever)
Also they have a lot of bundles but this is valid only if you have a lot of software that are not necessarily usefull for all users but that can be usefull for some specific categories of useres.