Personally, I think a Dom who subbed some time before would be better able to deal with the bad things that come up. Knowledge of "when he did this, I did that" would assist in understanding how the sub might respond, how to prevent negative reactions, and how to work towards appropriate ones.

Being able to get into their sub's head is essential in a good D/s relationship. It seems to me that those who just demand a knee-jerk reaction, rather than a constructive response are the relationships which don't last.

As with any other good interpersonal relationship, it must be worked at constantly to be effective.