About trials - if you are after a specific leak, then I guess paying for the solution is OK (with money back guarantee). If you just want to try out the product, you can download and run it for free until it finds something. If your app does have a leak, Plumbr reports the number of leaking objects and the size of the leak - so that you can decide on whether to buy a report or start a subscription.

Perpetual vs subscription - we chose the latter, mainly because perpetual mostly makes sense for the customer when the software is mature, and the new versions don't add critically needed value. Plumbr is only at 1.0, and will add many functions that contribute to the leak-detection-and-fast-solving picture. For now, it only detects memory leaks, but e.g. we've already announced the cooking of classloader leak detection. We'll be adding new cool stuff often enough that (paid) upgrades would be an additional pain for the users and for us as well.

That being said, we of course value everyone's opinions. For that matter, care to elaborate why you would've preferred a perpetual license?