Why 30?, that just seems like a strange number.

Assuming 8 hour work days, 32 seems a more obvious choice. You get 1 day/week off.

I've always started at 40, then negotiated down to 36, then to 32 at the same salary whenever offered a raise. If you're having a hard time finding a job, maybe tough it out for a year then negotiate for less hours when you've proven yourself. Obviously helps to be working for smaller companies which tend to be more flexible.