Red Baron:
The stability of the mine after it is abandoned is controlled by a lot of different factors - including whether or not the mine then floods. There have been mines that have been re-entered years later that are still stable. Caves are an illustration that openings can stay stable without human intervention. In large measure it depends on how large the pillars are when the mine is abandoned. In areas that have been longwalled the roof has collapsed already, and those areas cannot realistically normally be revisited (though they can if you are doing multi-pass extraction and had filled the empty space with waste - though this is quite rare). It also depends on the ways in which they held up the rock over the roadways,