During my first year or two I was almost "religious" about doing CG but when I had to travel to an even more humid climate than here (and no central a/c...) I had to use a styling cream with dimethicone, was the only thing that tamed frizz; still I probably only shampooed once (during the first week) and I was there for 6 weeks. I just used a white vinegar rinse each time I CO-washed (every other day) and didn't have any build up so I don't think one day of using them can be worse than that. My CO had essential oils though, the terpenes in many of them break down silicones and plastic resins from styling products.
This year I've been using silicones occasionally, it seems once I left my hair color on too long and my hair started to get frizzy and sometimes I wanted 2nd day hair and they helped. What I have done is rotate my COs and clarify if I'd used the 'cones 2 or 3 times in a given week.
However, I didn't like to hear that you had to straighten in order to maintain a prejudice in the "corporate world". The way I feel is that it'ss made up of people, just like you and me. and the only way they will get over that is to realize and accept that the majority of people are born with some wave or curl in their hair and there isn't anything wrong with that!
2A/3A, medium length, layered, colored dark/medium ash blonde - "CGer" since April '02.
"Converting the 'curlskeptics' one curly head at a time..." HWHC