Depends alot on the timeframe. If I'm expecting big economic boosts on a short term (founding new cities, building a market etc.) then I will wait.
However waiting has drawbacks. The unit costs maintenance. And also, gold you earn now can be used now to benefit you now and thus pay off on the longterm. Whereas gold later will only pay off later.
It also depends wheter I can use it in conflicts (even when I don't really need it). I usually prefer not to wait long since I tend to forget