Studio Performance: 6.5.4.9
No we can not shorten or reduce the run time of an Audit test because, Audit Tests run Scenarios one at a time in single, sequential sessions.
i.e. Total Time of Audit Test (which has scenario A and B ) = Load time of scenarios (Load time for scenario A + Load time for scenario B) + Run time of scenarios (Run time of scenario A + Run time of scenario B)
From the above example, we can concur that there is no option which we could alter or modify to reduce the time of an Audit test.