Re: Best Practices for tracking the effort to retest
The run information will give you an idea of how long the test originally took to run.
In the Test Lab module, find your test, in it's test set, and double-click on it to get the RUN information (Test Instance Properties)
Looking at "All runs" (of this instance)
The execution date/time are shown at the bottom of this form. if you expand the iteration you'll be able to see the timestamp of all the actions in the test. the execution time can be derived from this.
..I'm sure there's an easier way, but that'll give you some ideas..