I believe it depends on your procedure. It will be longer after periodontal plastic and esthetic procedures when you completely suspend mechanical plaque control. You should however be conscious of the side effects viz stains, altered taste , calculus formation and the more serious parotid bswelling.
Chlorhexidine Gluconate 0.12%, 10 ml, daily for 1 week reduces MS markedly and LB somewhat after restorations completed. Repeat every month.
Featherstone JD, White JM, Hoover CI, Rapozo-Hilo M, Weintraub JA, Wilson RS, Zhan L, Gansky SA. A randomized clinical trial of anticaries therapies targeted according to risk assessment (caries management by risk assessment). Caries Res. 2012;46(2):118-29.
Ans: There is no definite documentation in the realm of dental literal regarding the ideal wash out period of chlorhexidine mouth wash. Most of the studies state that a wash out period of one week is adequate.