Just sell me a bucket of gigabytes and I’ll consume it via as many devices as I want, then pay for another bucket when I run out.
Network congestion should be managed by towers anyway, not by artificial limits on number of devices or expiring data.
I like the flexible plan because I'm almost always near wifi, and thus my bill is often just $35 or so, but the bill will never be over $80 even if I were to have my phone downloading 24/7. MVNO mostly on T-Mobile network. It seems that Google has a better MVNO deal than many others, less slowdowns.
Fi deprioritizes after 15 or 50 GB/month based on your plan, though. I mostly don't hit that, and even if I do, I've never really noticed it -- I'm in a low population density area.
See "Shareable data included for tablets and other devices" in https://fi.google.com/about/plans
Fi looks interesting though, will look into it. Thanks for sharing.
EDIT: typo