Test images don't autoupdate. If a chrome developer never reimages their Chromebook then at some point ToT chrome will become incompatible. We can't predict when or how -- incompatible D-Bus changes are common.

Instead, print a warning if the remote device is 50 (or maybe 100) revisions behind the SDK.

At 3 revs per day that's about 2 weeks (or 1 month if we go for 100).