I ride once a month and all my HT2 BBs are perfect and have lasted over a year. Bear in mind that I do ride mainly in the dry and maximum ride time rarely exceeds two hours to preserve expensive components, but I have to say, based on my experience, outboard bottom brackets absolutely rock. Etc, unsubstantiated blah.
Oh, while I remember, back in the real world, my Acros Stainless Steel one seized up sitting in a cupboard after around two months of hardish use including a week in a very dry Pyrenees - it's going back to 18 Bikes next week. My mate killed one in the space of about a month including a muddy 24-hour solo. Not all they're cracked up to be ime. I also had to pop the seals and totally clean out the bearings and re-grease on a Hope stainless one on my then gf's bike when it started graunching. Since then it's been fine though.
Also found the Enduro replacement bearings disappointingly crap and badly sealed too. Lastest Shimano has managed six months before death though, with heavy regular use, which is a record for me. SLX btw. Essentially I think the system is just flawed, but there you go.