I use a sulfate shampoo whenever I color my hair which I have to admit is about once ever 2 weeks (I can't stand the grey). So before I color I use cones because I know I'll be washing them out with the sulfate poo.
I think once in a while is fine. My hair seems to be OK with this regimen. Probably the hair dye is worse than the cones! But I think the Mhen's snickers metaphor is correct - once in a while is fine - a steady diet of cones and sulfates probably isn't great for most curlies.
Let us know what works for you.
2/c and some 3A. Modified CG.
Highly porous. Color over grey.
Best 1st day method: Super Soaker
Conditioners: Curl Junkie Beauticurls Strengthening Conditioner,
Deep condish: Curl Junkie Curl Rehab
Stylers: Experimenting with cones & sulfates while the dews are high. Sometimes try roller sets - classic glamor but I prefer my curls.
Every day is a gift