I'm the lead on a project that has been underway for about a year and a half. Two of us have been working on it. One is the database guy. I'm the javascript/ui guy. Which is to say, essentially no overlap in code knowledge.

Here's the thing. Someone is about to offer me a sweet job with a nearly 30% bump in pay. Though I am perfectly happy with my current job and love the project, the new one would be better and I can't imagine saying no.

The big problem is that my project is supposed to go into production starting in a few weeks. I will consider the new guys to have disqualified the new job by being bad people who would ruin my life if they won't cooperate and let me start after deployment. Since they seem like decent, ethical people, I don't expect that to be a problem.

The current project will be brutalized by my absence. I take some comfort in the fact that I have emphatically requested an understudy for at least six months. That puts a little of the responsibility on the boss's head, but still, it's going to be a really bad thing.

What do others of you do when you are a critical to a project when it's time to move on? Do I owe any obligation to stick around even though something better shows up? I know my spouse would object if I found someone else. Does that apply to work?

I do have an understudy now, though he's fresh out of college. He's not going to replace me anytime soon. It's a small shop and the boss is going to be crushed. I am traumatized in anticipation of telling him and feel guilty about the practical consequences.

I'm looking for some solace and some strategy about how to deal with this transition.

Thank you for listening.

=========================Subsequent notes =========================

@ChaosPandion, Chance: No, I can't stay to finish the project. I will insist on a compromise where I finish the current sprint (about a month from now) but there is at least a half year, probably a year of solid, full-time, work still to be done. I wouldn't expect the new employer to hold the job that long.