This is what I am doing (business to consumer) and I am quite happy with it. I am maybe a bit too generous with the free credits (many people can use the service lightly for over a year on the trial) but I like that they get the exact experience as if they were paying and they can pause and resume their trial with no extra complexity on my end. Just sign up and you get some starting credits. Then you can just buy more as you need them. I think it makes things simpler and avoids any sort of pressure.
Sometimes there's a shifting business priority, and guess which wins when the choice is "important customer X is on fire" vs "our developer trial for wizbang component xyz is going to expire in 8 days".
