maintain the seam tape. If it starts to peel back, re-glue it or replace it. Of course, keep it out of the uv for as long as possible. Make certain that there is no moisture trapped inside the tubes. Clean it well and dry after trips and 303 like you are doing.
As for storage and transportation: It is probably best to store inflated, but I feel like the difference is negligible for hypalon. Transportation is a different debate. I have seen more damage happen to rolled rafts being loaded, unloaded, pushed, dropped, ect. than I have seen to trailered rafts, but road gravel, dirt and additional uv exposure are concerns for transporting trailered rafts.
Personally, I feel like a hypalon raft is built to be very tough and I just do what works best for me. I don't have room to store mine inflated over the winter, and I like being able to float my already rigged boat off my trailer at the ramp and get on the water quicker.