[toumhi]

> Generally, though, you want the time period to end after the user has seen the benefits and before they have exhausted their initial enthusiasm or encountered any bugs.

Corollary: do not end the trial, whether it is time-limited or usage-limited, if the user couldn't verify the expected benefits before it's over.

For example, at my company, we help vacation rental owners to publish their property on multiple websites. We've learnt that 1 month was, in fact, too short a trial for people to fully appreciate our service (for reasons that would take a long time to explain here). YMMV.