You actually keep it stored in that huge honking tube container?I have a lid on mine that I notched out for the sous vide. Evaporation is a non-issue.
I got it years ago(2009) on an Amazon sale for about $80. It's hard to say when it lost it's edge. When I first got it is was stupid sharp, after awhile it behaved like any other knife and no amount of honing would change that. Shun reinstated their free sharpening program and I sent it in, and it came back sharper, although not like when I first got the thing and that didn't last long at all.Ancient, what did you pay and how long before it stopped holding its edge?