Heh, now that sounds like a joke :)
Decided to look on the Russian-language forum where BLtoolkit originally appeared and found MY OWN 5 years old topic about the same problem: http://www.rsdn.ru/forum/prj.rfd/2966573.flat#2966573
Since that time solution was already implemented, that is another attribute: InstanceCacheAttribute
:) Good luck! :)