My general rule of thumb is, unless your work environment is really causing a big negative impact on your life, time your exit so it doesn't screw someone else's life up even more.

That said, the end of a project during or after a production launch isn't necessarily a bad time for this. I left my last job the exact same way. Unless you were the only person on your team with any experience of knowledge of core components (which means it wasn't a well structured team anyway), it can work out fine.

In my case, I had done 100% of the payment/billing system (but 1/2 others knew about all the requirements from the planning stages), and probably 75% of the devops + automation (fully automated infrastructure provisioning and updates). It worked out fine.