...Really? I find age brings out the sweetness more as the hops fade. The level of sweetness has more to do with how balanced the BU-GU levels are. Also the amount of dextrins and crystal malt used. If the hops aren't in balance to begin with it will only get more cloying with age...
Well maybe... but not always.
In my own experience with making barleywines, I've had many of them a year or more old and even the less hopped renditions didn't get sweeter with age; the sweetness faded (not in a bad way) into what I can only describe as a deep, richness of malt, with some residual sweetness.
To a large degree, it boils down to one's individual perception and also as you pointed out, the methods used to make it.