I've been working with Drupal since 4.6 and was somewhat involved in the process of making 4.7. That was about 8 years ago. Here are some truths I've learned in that time.
There is at least one arc to people's involvement: people go up and people go down
Think about your involvement in Drupal. Did it start at some level, stay at that level, and continue at that same level indefinitely? Probably no. You are somewhere on an arc of involvement. You may be on a mini-arc within a bigger arc. When you first heard of Drupal you didn't immediately jump in and file bug reports and help do usability studies and write documentation. You tried it out. Then you did a little contribution and you liked it (or hated it) but your involvement probably kept increasing for a while. Right now maybe you're headed up or down - maybe you're involvement is decreasing right now because of a big project at work but you know it will increase 2 months from now because your next project will make it easy to contribute to a given module (or core?). Let's look at some real world arcs of involvement.
Let's look just at Drupal Core involvement. I've used the data from marvil07 which includes analysis on commits to the main branch of core (originally CVS and then migrated to git) since 2000. Here are the top committers for the years 2000 to 2003, inclusive:
|natrak (pseudonym of Kjartan)||82|
Holy cow. I only recognize 8 of those 13 people, but they are the foundations of Drupal for the first quarter of it's life. Let's look at the next 3 years: 2004 to 2007.