What the tires need is air circulation and drainage for extended periods. Crushed gravel would be my first choice. I don't see any harm coming from leaving the tires on pressure treated lumber for a month or three. Dealers leave the trailers sitting around for years on asphalt or dirt.
2010 Cedar Creek 5th Wheel 34SATS "The Beast"
2006 Ford F350 Lariat 6.0L Diesel
2003 Harley Heritage Softail "Hogzilla"
1988 Harley Softail Custom "The Fireman"
1986 Marriage to "Wifey" (patience of a saint)