The problem I have with the annual subscription model is that you have no idea what, if any, new releases will be issued during your subscription period. Developers make no guarantee. And if the renewal price is exactly the same as the initial purchase price, there is little incentive to renew.

I've often purchased software based on this model and have received only 2 or 3 minor updates in the year. Then at renewal time, I'm expected to pay full cost again. So, I rarely do this. Most plugins will work for at least a year without updates so I typically buy a year, skip a year, buy a year etc.

The way I look at it (as a developer myself) is that the initial purchase price should cover the cost of developing the software and the renewal price should cover the cost of updates.

If renewals are adequately discounted and I have received a decent number of meaningful updates in the previous year, I keep my subscription running.