I don't think this solves the problem of people getting distracted. If I make 10 API calls and then get called away to do Super Important Thing for the next 6 d

I don't think this solves the problem of people getting distracted. If I make 10 API calls and then get called away to do Super Important Thing for the next 6 days, I'm probably pretty likely to give up on a service if my trial period is reduced to 1 day. Have you thought about N API calls for a trial? That's what I've used for API-first products in the past that worked pretty well for me.