I watched an interesting video on You Tube about this and the guy used only baby powder. Not only did he put it on his outside seals, but inside as well. [while the slides were in]. They said most slide seals malfunction because they "stick" to the outer wall and tear or get pulled out of their grove. Personally, I use a silicone rubber treatment spray on my seals. I might try the baby powder treatment as well, especially if I have to store it for longer periods of time between uses.
2012 Eagle 320 RLDS
2012 Ford F-250 Crew Cab FX4, 6.7l PSD
3.55 E-locker, Timbrens