I'm an older person and I've only heard the 'think' version. 'Thing' is a mis-hearing.

Very well researched, Will. I concede defeat.

Robert: yes, there are many regional accents but I was assuming standard pronunciation for both the UK and US.
As for 'owrally' I was imagining a rhyme with 'cow' (see palaceuk) but even a rhyme with 'blow' would be odd.
Perhaps Aussies could clarify.

We British pronounce them the same. Americans say 'au' differently from us. To a Brit the American 'au' sounds like 'ah'.
The Australian 'owrally' is impossible...

Thanks, Erin, for that post. I wondered where you lived.
I guessed that you had succumbed to the American language when I saw a capital after a colon. (Just kidding.)
To me, 'Jane and John' is not a noun phrase. They are just John and Jane. Americans are at liberty to make changes to their form of the language so long as they don't then claim it to be 'standard usage'.
Of course you're right about the language changing. Dr. Johnson said it best in the preface to his Dictionary:

"...to enchain syllables, and to lash the wind, are equally the undertakings of pride, unwilling to measure its desires by its strength."

That doesn't mean there can't be a spirited debate. It's true, of course, that King Canute is my role model....

Re: 'Jane and John's house.'
If this is standard usage, it must be of recent date. It sounds barbarous to me.

If there is an example of a reputable British author using this form more than say thirty years ago,,,,,,I would be intrigued.

Erin - a couple of suggestions.
One can't say 'me and my sisters' childhood' because that means you are saying 'me childhood'. Also I go by the rule that it is polite to put oneself last. 'My sisters' childhood and mine.'
As to Jack and Jill's house - well, that is becoming modern usage. In the past, you could use one apostrophe for a company, for example Marks and Spencer's. There, one apostrophe does duty for both. But individuals need two. Otherwise one has this sort of confusion:

"I met Anne and Joe's aunt at the airport."

How many people did I meet? One or two? Please! Separate apostrophes!

Some writers aim for a stripped-down style. Others like to enjoy the richness of the language.
I'd say that it's not about adverbs per se.

"Must not head mobs?"
Will - what does that mean?

In British English both words are used. I wouldn't say that 'farther' is seen as old-fashioned.