I am natural and I use Porosity Control right before I color my hair. It helps the color to "take" better...more evenly I guess and to lessen damage/dryness. I think relaxed ladies use it after a touch-up to bring ph balance back to normal....
ETA, not sure how often it can be used, but I initially thought it was only to be used during different chemcial services (coloring, relaxing). I guess usage will vary across the board for those who use it....
Roux who makes Porosity Control also has a deep moisturizing conditioner called "Moisture Recovery" that I used this weekend (it comes in a little pack and was about $1.29). I had good results with it so I plan to add it to my stash of deep conditioners while I am on the deep conditioning and steaming challenges.