My first question would be what are you trying to achieve for your hair when you're deep conditioning after a conditioner wash? For my hair that would be too much conditioning. If have build up I would clarify first, follow with a 45 minute deep conditioning treatment, leave in, and then style.
But I guess you have to try it first to assess what benefits if any for your hair are provided. Are you currently co-washing before deep conditioning? What are your results like?
No, not unless something's wrong. Usually I rinse my hair then DC and rinse again. That's what I call a co-wash. Now, if something's up I'll rinse, poo, pre-poo, DC, rinse.