The OP may gain from looking at the classic tricks done to minimize disk writes with older CF cards on OpenBSD 3.7:
http://blog.innerewut.de/2005/05/14/openbsd-3-7-on-wrap
http://blog.innerewut.de/tags/wrap/
http://www.kaschwig.net/projects/openbsd/wrap/
Yes, these blog entries reference an
old version of OpenBSD, but recent traffic on
misc@ has pointed that they are still valid. I used them as a reference when configuring a 4GB Eee PC to run OpenBSD
-current.
FWIW.