Long running workflows, moving from DB to DB

With a workflow that runs and sits running, say for 1 year, and you want
to upgrade your User App DB.

Most people have found a UA upgrade is a disaster, so it is intensely
simpler to simply install a fresh 4.72 and then put your DAL and PRD's

So if you wanted to copy out the running Workflows from the old UA's
database and copy it into the new DB,any ideas on how you might approach it?

I recall reading in the docs at one point that during an upgrade like
this you might want to copy out of the DB and then copy the contents back.

Anyone ever tried it?

I was thinking maybe querying over SOAP to getWorkEntries, then getWork
for each and then restarting the workflows. Thing is getting the
timeouts to match so that anything due is still due at the same time.
(I.e. If it is due 90 days from start, vs due at a specified date sort
of thing).

Any other options?