But now it's actually being produced and put into products.

There are probably more asterisks than starts inn that statement.

Is 20 years the average? The maximum under ideal circumstances? What would be the effective capacity of the battery at 19 years? What is the maintenance required?

And I would walk 500 more

Where would you drive in your phone, bro? Don't be silly.

Based on the article they are more expensive than li-ion batteries (for now), so probably not yet. And the article doesn't mention anything about this, but I imagine there would be scaling issues.

Do you know how big and heavy that phone would be with a car battery in it?

I don't think solid state batteries provide as much benefit in smaller devices.

Size constrains probably.

According to Samsung SDI's VP, automakers are interested in its solid-state battery packs because they are smaller, lighter, and much safer than what's in current electric cars. Apparently, they are also rather expensive to produce, since it warns that they will first go into the "super premium" EV segment of luxury electric cars that can cover more than 600 miles on a charge.

Apparently not, though this is all marketing speak