I have submitted my retirement notice.  The suggested an end date is June 30th, though I'm willing to work with them to hire and mentor my replacement.

I've been mulling retirement over for a while. Late last week I was asked to put together my org's long term compensation budget (Compensation paid out over the next two years) By announcing my retirement now my boss can allocate my future long term compensation to other people-- give them a little raise so that maybe they are more inclined to stay around after my departure. 

When I met my boss this morning to discuss the budget, I informed him of my decision. He sighed. He quizzed me a bit. We talked a little about the budget. Mostly we discussed my future plans and what changed that I decided to pull the trigger.