I'm a young arrogant dog and I think sports =/= martial arts and vice versa.

And yes I DO think that one outrules the other.

As for OP questions;

- Would you hold a person back by virtue of time-served alone even if it's evident they are proficient enough to move forward?

Yes I would. Patience and humility are just as important, for some people even more important than martial technique. Moving forward isn't getting a ''higher rank'' moving forward is supposed to be daily training and improvement of oneself and the martail arts you practice.

- Do you consider prior martial arts experience when someone joins your club when placing them in a class (for instance, beginner, intermediate or advanced), or is that irrelevant? Why or why not?

It depends entirely on the ''experience''.. I've seen people come from other styles with high ranks who in reality didn't know and couldn't do anything practical ''theoretical martial artists'' as I like to call them.

Then there have been some who have BBs or higher in other styles that do deserve those ranks but are lacking many of the techniques in our style typically those people may lose a rank or two but climb back up to them very quickly or we just don't care and let them keep the rank as long as they practice with heart to learn our styles techniques.

- Is "time-served" set in stone, or is the fitness level, prior athletic experience, natural ability, rate of learning, etc. an important thing to consider?

Set in stone. I think people who practice martial arts for the sake of martial arts and self improvement should have these requirements. The ranks are irrelevant to me but most people who genuinely pratice for practice still care about them so having time requirements makes sure that the practitioners don't rush through the basics just to get a prettier belt and so on. As I also said it's a test of patience if someone just wants a BB they can go do Olympic TKD or buy it on ebay.