Node-red MQTT QOS does not work?

[jbudd]

Sorry Steve, I only just noticed your reply.
I'll have to do some more reading on mqtt 5, was not aware of session expiry vs keep alive.

I was looking at another thread https://discourse.nodered.org/t/edge-to-cloud-computing/79815 about making data transfer resilient over network drop-outs.
I thought "Surely MQTT already does this?" but it seems not, except with the single most recent retained message (per topic). Hence this thread.