The only answer that jumps out in my mind is that they don't care about your quality of life. If they did, wouldn't they hire you on full time with full benefits?

There are definitely some exceptions to the rule (they tend to be smaller rather than larger companies though), but by and large companies will do nothing but beg for your unswerving loyalty without ever caring about your own personal quality if life or committing any loyalty to you at all, at least not until you start getting into the upper half of the corporate ladder. You are as replaceable as a nut on a bolt. Your company survived just fine before you and they will survive just fine without you, and they know this. If you leave people will talk about it for a week but within a month people will barely miss you and a year later it will be a rare thing for someone to speak your name.

I am not trying to be super negative, I am just trying to be very real with you. I am currently in a different but similar situation. I had a similar conversation as you're describing with my boss last week. I am trying to get a raise or a promotion, both of which I've earned and am overdue for. I have been with the company three years and have done a lot of good work for them. I have just hit the ceiling unfortunately.

So what I am doing is working hard, collecting the paycheck, stashing savings, and figuring out where I'm going next and when I'm leaving. I'm not saying that you shouldn't try to re-negotiate, but my concern for you is that this is going to put a star by your name and could impact your longevity with the company if that is something your are hoping for there. I don't care if they star my name - I was 90% sure I was leaving anyway before I had the conversation, but I at least wanted to give it a shot. If you think are are going to leave, then it's probably not a big deal. I just know that every company I've ever worked for when I try to get a better deal for myself they don't want to play along and that always seems to mark the beginning of my swan song. I just don't ever do it as early as you sound like you are going to.