I'm trying out Flow, the task-management app, and I must say I'm pretty impressed. The problem is, Flow comes with a 14-day trial, and I'm on day 14. Even though today is only the second time I've logged in and the first time I actually created a task in it. So now I have the dilemma of deciding whether to subscribe based on a few minutes usage. If I hadn't gotten around to logging in today, that would be based on zero usage, and I definitely wouldn't subscribe.
This Quora thread discusses the question of whether a 15-day or 30-day free trial works better. (Quick version: It depends.) But my Flow experience made me wonder: Why is the norm to limit by time at all, rather than actual usage? For example, the number of times you've logged in—or, in this case, number of tasks created.
The answer could be that limiting people's time to check something out forces a decision and increases sales. (And someone's probably tested that.) But as a user, it would be refreshing to see something that let me assess a product on my schedule. And, who knows, maybe more people would get into your awesome app eventually.