In my experience, semi and Demi permanent colors seem not to "wash out" as they're supposed to, but instead change into funky colors on gray hair. I think that's why most people with a lot of gray use permanent instead. I've read on gray boards that the Demi color never washes out, so all you're doing is extending the time it will take to transition. For me, the choice was easy; get it over with as quickly as possible. Cold turkey.
2C/ Coarse/ Normal porosity/ SW Florida/ Transitioning to gray
Cleanse: CJ Daily Fix, JC Cleansing Cream, TJ Tea Tree Condish
Condish: JC Too Shea, CJ Curl Rehab (both as RO & LI)
Stylers: UFD CM, CJ PP, JC Spiralicious, Darcy's Cream Gel & Cocoa bean whip