Members who've had a couple of weeks of full access without subscribing are timed out and moved to a read-only group. We use notices and messages to nudge that group towards subscribing, but this add-on has worked better than anything else.
I don't leave it on permanently, as I think that would frustrate those members and drive them away. Instead, I switch it on for the read-only group every so often, roughly one weekend in three. It's been very effective at converting large numbers of them into subscribers.
An excellent add-on. Highly recommended.