Most modern computer fans are designed to be used in almost any configuration. Trust me, you'll be fine using those fans horizontally, and you shouldn't have any problems with the bearing.
It says in the soec sheet it has a mtbf of 50000 hours, typical of a sleeve bearing. And I know that sleeve die quickly when mounted horizontally. The only possible other bearing I think this fan use is the cheap rifle bearing which can be used horizontally. Anyone have open this fan confirm me?