To answer your question, it's not about how much you do but who you know and your abilities.
If you can motivate, kiss enough ass, and have "connections" or "know someone or knows someone who does" then you are a shoe-in.
The WT could care less about seniority or how zealous you are. It's a numbers game and if you can help the bottom line then you qualify.
Sad but true. I know of some brothers who have been spinning their wheels for years trying to be the most spiritual person in the org. yet they remain like that for years. What a joke.