Thanks for clarifying again. I had missed that.
I see the option in the schedule, but it's only a checkbox. My guess is you have to combine it with the Settings -> Advanced -> Full Backup Interval input? It's not clear from the docs if those two things are related or separate.
I have mixed feelings about the deltas. There's clearly some thought on the part of someone that someone may need to do the deltas-forever thing due to the ability to create an initial seed for a remote site due to bandwidth constraints. In my case this is a remote NFS store, but it's a low latency (~5ms) and high throughput (1Gbps) connection so it's not too onerous to do a full periodically.
At the end of the day, I've ticked the "Force Full Backup" checkbox and put a value the same as retention in the advanced settings. We'll see how it goes.
I'm still puzzled by why this is a recent issue and didn't used to exist. Also it would be nice if there was some graceful timeout or something that will kindly bring the replication to a close in the event that no data is being transferred for a prolonged period of time.