This is relevant to me. I have one archived machine that hasn't backed up for 2.5 years and another one at 4.2 months. Last backup report still shows it though. Unfortunately I accidentally removed the whole machine for the former one from my local backup a while back. Fortunately the Crashplan Cloud backup was able to be restored by Crashplan (good support there once I got them to understand the problem). I couldn't restore my local archive though.

I also was not aware of this change. It does seem to me at least that this came in under the radar. Crashplan don't spam with weekly updates or similar so had I received an email covering this, I think I would have read it.

If I got 5 days notice, I'm not sure what I'd do. Speeds aren't fast enough so I don't think I could download the machine in 5 days. I still lose its history too. I guess I'd just create a fake machine in a VM or something to reactivate the machine.