I think a good rule of thumb is lay your intentions out there ASAP, and give the company (and your co-founder) the time it needs to adjust to your departure, wi

I think a good rule of thumb is lay your intentions out there ASAP, and give the company (and your co-founder) the time it needs to adjust to your departure, within reason. At the end of the day, this is about you. If you're leaving to do something that will make you happy, no one with sense can hold that against you.