Measurement techniques of water vapor transmission rates (WVTR) through barrier materials were actively studied recently．
WVTR of 1 x 10-6 g m-2 day-1 is accepted to be a standard for the packaging of organic light emitting diodes (OLED) for commercial use.
http://www.printedelectronicsworld.com/articl...evaluation


"In order to achieve device liftimes of tens of thousands of hours, water vapor transmissions rates, (WVTR) must be 10-6 g/m2/day, and oxygen transmission rates, (OTR) must be <_0-3/>
http://news.sys-con.com/node/4115814

.....Go QDX, (and maybe film not required)