Just chiming in with the 'relationships are a work in progress' sentiment, I'd add, so are people. Or, certainly, so am I. :) A lot of my 'deal breakers' only developed after earlier relationships in which I thought "ooh, I can cope with that" only to discover that no, in the long term, I couldn't. So I suppose my 'deal breakers' evolved, but they were never laid out in a discussion where the two of us brought lists to the table and started ticking things off .... I think I only recognise them in retrospect!
My requirements for 'a date' were pretty much 'funny liberal type, non-smoker, interesting conversationalist, someone whom I find attractive.'
My requirements for a 'boyfriend' were 'similar views on religion, similar interest in levels of relationship seriousness (e.g. if the boyfriend I'd had aged 20 had said "I want to get married in the next few years" I would have run! But the one I met aged 26 who said the same thing... well I was on the same wavelength by then, and we got married 2 years later), fun in bed, relatively sure of self"
My requirements for 'serious boyfriend' then included "likes dogs, likes and wants children, good to live with (cleans, tidies, cooks, does these things without being reminded), similar political views, active feminist, a couple of hobbies in common, likes my family'' ... and again, I don't know how many of these I could live without, because I happened to have the luck to find lots in one person at about the time I'd worked out what I wanted in a long-term partner.
Imagining for a moment that my wonderful H got hit by a bus and I had to date again (oh god, no!) I think real, honest-to-god "I'll get up with our son and walk out" dealbreakers would be things I imagine I'd discover quite far into a relationship but would make me actually leave:
Addictions (I don't care for smoking and wouldn't want it around my boys, but I think alcoholism, drugs, or gambling destroy families much faster. Any of these would be a 'nope, sorry, not in my family' dealbreaker).
Difference in opinion about childraising, specifically discipline (eg: smacking, or even just mocking, swearing etc)
Bad with money (eg spendthrift or extremely stingy)
Bad attitude towards women or other people less powerful/privileged
I imagine stuff like 'doesn't share similar political views' and 'unfeminist' would be something that I'd notice before I was in an established relationship with someone, as I tend to mention that stuff in conversation!