If I had a 2 week trial - those that submit web extensions to stores rarely wouldn't see the benefit of the product before their trial was over. I made it simple and capped it at 5 successful submissions. Success is important here because you can go through the review cycle 5 times ('5 failed submissions' - this number could change, but it works for now) and then your trial would be over. At the end of the day, regardless of how fast teams work, I want everyone to see the value under the same conditions.
I've worked at places that are focused on time trials because there's no practical way to limit the product in another sense that would give users time to fit in their workflow but also limit their actions enough to convert. Perhaps that's a failure of the scope of the product etc. but it works well enough for them.