My non O expires on 21 January and I have until 22 March on my latest entry. If I make a border run on 19 January will I be able to get a 90 day entry stamp as I have heard rumour.

Thanks!

Yes. Enter before the Visa expires and get 90 days. Providing it is a Multi Entry.

Yes, as long as the VISA is valid, you will get 90 days on entry. Your visa is still valid on the 19th, so no problem.

But that is only the case if your VISA is valid, in essence if you have a multiple entry visa, which requires you to leave every 90 days. Not if you have a singl entry vissa.