What's the longest you've waited before approaching a girl you see regularly in person?

There's this gorgeous girl who goes to my gym and I see her there quite often because we usually go at the same time. We've exchanged a couple of glances/smiles here and there, and we've also spoken a few brief words when asking if the other person is done with a specific machine. But I've never asked for her name or displayed interest in any way because I'm scared about making things awkward if it doesn't work out and we have to keep regularly seeing each other at the gym. At the same time, I want to approach her anyway, but I'm also worried that if I wait too long it'll be awkward when I finally do it . Has anyone waited for a long time before finally mustering up the courage to approach a girl, whether it be at work, in class, at the gym, or somewhere else? How long did you wait and how did it go?