Check out this link to a post on gotmead.com
In his post, he basically explains how bulk aging can be beneficial for four reasons:
1. It's easier to see what's going on in the carboy than in a bunch of wine bottles.
2. It's easier and safer if you need to alter the brew if it's in the carboy.
3. The temperature and environmental variables won't have as much of an effect on the large carboy as they would on small wine bottles.
4. Something about esterfication
4 again. You'll drink less of it if it's in a big carboy then if it's "aging" in wine bottles.
Of all of these reasons, my personal experience would lead me to agree with his second number 4 reason. I can never seem to stop myself from drinking something that is already bottled up for more than a month but, if it's in a bucket or carboy it's more of a pain to get to so I typically leave it alone. Also true when friends come over and want to sample my latest concoction. They'll be less likely to want to drink it from the buckets sitting in my bathtub for some reason...