If I setup a BYOD export job with DMF, and schedule it to run say, every hour, but for some reason one of the exports takes over 1 hour, then a second instance of the same job kicks off regardless. This then attempts to export the same data but with slightly less resources. This will undoubtedly also take over an hour, so the problem compounds.

There is an option on the "Export job in batch" window for "Run Sequentially" which might seem related, but it doesn't appear to work for exports.