How long would you wait?

I am currently in waiting to hear from a job I interviewed for 3 weeks ago. This position would be my dream job, and I feel positive about the interview, except for the fact that it has been 3 weeks. After 1 week, they began checking my references, then I followed up at 2 weeks and was told by the manager that she was still "working on the positions." Now, just 2 days ago HR called to say "We didn't forget about you, but the manager is still interviewing, and I was proactive and went ahead and completed your reference check." So that is where I am with regards to that position.

My dilemma is that I currently work part-time and perdiem, and really need more hours, to make ends meet. I COULD tell my current boss where I am per diem that I would like to change to a part-time position, so that I could guarantee my hours. Of course, I don't want to ask for this, only to hear from the "dream job" two weeks later, and have to back out. I'd prefer not to burn bridges, but I would if this job came calling.

So how long would should I wait to hear from the dream job? I was giving up hope, until this spontaneous HR call (not in response to a follow-up from me), but I really need to increase my hours, like a month ago. I kind of want to follow-up with the manager, but since I've already done that once, I'm kind of lost as to what I should say, and when I should do this..

Thanks for any input