"In my last job, I used to crash in the office most of the time (9 AM to 3 PM), skip most weekdays, work all night and all sunday. I never had any complaints and was considered quite good at what I do.

My last job was at Google."

In a company like Google, there are enough people in the office during normal business hours to compensate for the time you aren't there.

I can sympathize with the poster. If he (his co-founder) is the only person working on the technical side of the project, he should be there in the office during normal working hours.

When they do need to meet a client at 9am (because most businesses in the US are 9-5), will the developer be able to be there without falling asleep at the meeting?

It also shows me that the developer lacks discipline. The poster made a mistake in making him a co-founder. He probably should really be an employee.

I also get a sense that the developer wants to just hack away at the code on his own time and not have to talk to anyone about it. This is a recipe for failure. I've worked on many projects like this and what usually ends up happening is that the project gets finished with little or no input from customers/other people besides the developer and it fails.