I think that the manufacturers of RVs know what they're doing by NOT ordering gas filled dbl paned windows (although some offer it as an option). That's because, unlike a sticks and bricks, it's a MOVING HOUSE. And roads in this country are no longer thousands of miles of perfect. The bouncing around these things get not only cause seal leaks in windows, but also break chassis parts, loosen cabinets from the walls, throw dishes out of the cabinets, throw you in the air, pop lug nuts loose, etc.
I wouldn't waste money on gassing my dbl paned windows as it's a waste of time and money.
No offense, it's just that it doesn't make sense to me to put gas in the windows of an RV, because it's being driven and bounced around all the time. Many sticks and bricks homes windows with gas develop leaks just sitting there. I was a realtor in Oregon and saw the stains many times.