Good question. So one change I made last year was to cap the number of queues the free account could utilize. It's sort of hard to know for certain if that was what moved the needle though.

There has been a suggestion that maybe the free plan could just be a time-limited trial instead.

But it feels like there is some risk associated with that - as often a customer will use the free plan for (eg) six months, before hitting the limits and becoming a paid account.