Of course, Armory uses waaaay more than 128 bits of entropy, but I'll be bringing it down to 128 or 160 in the next release -- I was thinking 160 because I wanted to give a little margin in case your system does not have a high-quality entropy pool at creation time. This because I totally agree with ThomasV -- 128 bits is a nice, unbreakable value. Maybe in 1000 years when we have Dyson spheres around a few different stars for the purpose of collecting energy to break my wallet, they might break 128 bits.
I hope you where exaggerating. 128 bits encryption could be breaked "routinely" in 100 years. Armchair explanation: DES at 56 bits can be breaked "routinely" by NSA/CIA ecc. If Moore's Law is sustainable the number of transistors in a chip will double every 1.5 years. Let's say that every doubling in number of transistors double the speed (because, in the end, cracking a code is a highly parallelizable task, so doubling the number of processors WILL double the speed). So each 1.5 years the number of bits that can be cracked "routinely" is raised by 1 (double speed = +1 bits, because +1 bit doubles the keyspace)... So 72 * 1.5 = 108 years... But note that DES was cracked "routinely" some years ago.
(read for example here.
http://en.wikipedia.org/wiki/EFF_DES_cracker , in 1998 EFF brute-force cracked DES in 56 hours for 250,000$. So if Moore Law is sustainable, in 2106 AES128 could be cracked in 56 hours, but note that some years before a resolute cracker with some million $ and a month of time could probably crack it)