I haven't had a system running yet, but would never run RO/DI direct.
It isn't efficient this way and can obviously dilute your system if it fails.
I am lucky that I have a room where I can store 55g if need, although I will probably never hold that much at one time.
I just bought a drum/barrel
http://www.canreef.com/vbulletin/showthread.php?t=80884
Sorry if the add doesn't apply to your area
My plan is to have a 10g top-up for my 100g system. No direct plumbing.
trudge the water to my ATO as needed.