It depends on your profit target, unless you are a scalper, I find anything under a 30 minute noise. Although I have seen some nice 13/13's work on a 5 and a 15 good for a few. Demark's are really not consistant and need to be used in conjunction with other indees. Look at how many bad 13'S we blew through on the way from $85 to par late last year in crude.
good trading!
surdo