Increased capacity means the oil cycles through the engine less frequently and the oil can remain in the pan for a longer period of time.
Yes, that is true. However the actual amount of extra cooling is very limited and unlikely to make a significant difference in the life of the oil or to the operation of the engine. The information I've seen so far is that one of those oil pans might drop oil temperatures ten degrees at most. Ten degrees isn't worth spending almost a thousand dollars to have one of those pans installed, plus the extra cost involved in each and every oil change.
You mentioned 265° in a previous post. Was that coolant temperature, head temperature, or oil temperature, and how was it measured? I'd be a little surprised if a Twin Cooled bike was running the same kind of oil temp that has been fairly common on the earlier 110's, since the water cooled heads should make a difference.
If you use a good quality synthetic motorcycle oil made for air cooled engines, temps in the 230-270°F range are not a problem and I would consider that to be a pretty good estimation of the normal range for a late model Harley. Consult the folks at Mobil 1 or Amsoil if you think otherwise and see what they say. I know the people at Amsoil used to say 300°F was not a problem for their oil, but I think I wouldn't want my oil to run quite that hot all the time. An occasional foray into that range shouldn't hurt though.
Jerry