The IPAs perform better in competitions longer so there is some (allbeit not conclusive) confirmation that it has an effect (again no side by sides). It's just very easy to do. I am very sensitive to oxidized hops. I loathe a hoppy beer that is oxidized.
Also, when I say a couple months longer on my IPAs I mean a couple months longer than when I don't use ascorbic acid. I would say normally I get 3-4 months of good hop aroma and flavor in my IPAs... Then if I use Ascorbic acid It's more like 6 months or so.
I'm not saying ascorbic acid (or campden tablets - I've used both... Just prefer the ascorbic acid) is the only way to go... but for me with purging and transferring with co2 from 1 vessel to the next... I personally see a difference in shelf life (at least shelf life of beer I'm willing to drink). Once a beer becomes mildly undesirable to me I will dump it... There is always another keg waiting for it's shot in the kegerator (my kegerator only holds 2 kegs and I have just under 40 total kegs lol)
I think an experiment may be in order somewhere down the line though.