This is a subject with several opinions.

It's true that gold is harder to come by when you first begin, but is it really worth permanently having inferior units just to try and get somewhere faster? For silvers, I don't really think it matters that much since they get replaced anyway - and have smaller stat gains. However, I don't suggest CCing healers, Leeanne, or Phyllis early. These are silvers that can continue to be used for a very long time. Never CC gold or higher early.

But lets also consider that you don't need to CC any units at all to get to the good farming maps. I prefer Dragon Hunting over the others (until you can farm Immortal Beast) because of the gold efficiency you gain from combining higher level units. In fact, I have the video guides I made and posted here in the forum sticky. Contrary to what many others say, you don't need to CC anything to get past Castle Retake.

It's up to you in the end. It gets to the point where 30k gold is like pocket change. I'm currently sitting at over 9 mil. If you don't mind a unit being weaker than it could have been, or if it is a silver that is likely to get replaced anyway, then fine, why not. And again, I strongly advise not to do this for girls higher than silver.