I think an eyeball fit from an experienced fitter can be quite helpful. If the guy's got a good rep, it might help alot, at least to get you out there.

So many things can change a good fit, including time in the saddle.

Kinda depends on where you are in your riding, and what your needs and goals are. Dealing with pain or serious comfort issues, or wanting to maximize performance for an experienced cyclist would really require the more extensive fitting. An approximate fit might be just fine for dialing in a new bike, or fitting a new saddle or bars, or the like.