The restaurant in town closed about six months ago. For weeks, there was a sign about renovations. Then a new sign, this one promising big things. Then, of course, the "for rent" sign from the broker.
A software service I used for a while sent me a note today that read:
Please note that the service has reached end of life and is scheduled to be decommissioned on Monday, December 3rd. Once the service has been taken down, all content will be deleted. It is very important that you transfer your data to another service provider prior to this date to avoid data loss.
That's it. The entire note.
One last example: someone I hired a while ago changed her mind after the first day. She never showed up again. Didn't answer calls or email. Just vanished. Not dead, just a chicken.
It seems to me that you ought to say goodbye with the same care and attention to detail and honesty you use to say hello. You never know when you'll be back.