I am another one who is going to say YANBU.
This sort of behaviour is very selfish if the impact on the other partner is not considered.
My DH is also working stupid hours at the moment - seems to becoming the norm in a lot of industries now and people not on bankers salaries are still expected to be available 24/7 
However I was getting fed up with the last minute phonecalls where DH would ring at 8pm and say he was still at work and had no idea when he would be back. And that he also needed to work the weekend.
He would then get cross with me getting fed up and say "But I told you this was going to be a difficult couple of weeks as project X and Y needed completing". Conveniently forgetting that prior to this there was project A and B, and prior to that C and D and that I had worked around that and given him leeway...
So I sat him down and had a little chat. Saying that of course I would support him when he needed to work late and that I understood the pressures he was under, particularly in this recession [as the company he works for has made a lot of people redundant and there are thus less people available for the work required
]
BUT his working late and weekends also affected ME. I work part-time and the other half of the week at home with a 3 year old and 1 year old.
I was finding it difficult to get my work done, especially stuff that needed to be done out of normal working hours [client calls and such]. Was also exhausted at end of long day caring for kids and was craving him to walk in the door at 7pm for bathtime or for us to have family time [and practical help!] on the weekends.
The upshot is DH said he understood and made more of an effort to get home at a more reasonable time or to call me with more notice if he couldn't, so I could prepare myself for doing the dinner/bathtime/bedtime slog by myself.
And he only occasionally goes for drinks after work. He will ask if I am okay with that [as his absence and possible subsequent hangover/tiredness of course has an impact on me] and is usually always home by about midnight or 1am at the latest. I am absolutely fine with this. I know that DH in the main wants to be at home with his family, not pissing it up in some club until 4am...
OP in your shoes I would be pretty pissed off.
Let him know exactly how this is making you feel and that his behaviour is having a negative impact on you.
I agree with the posters who say he is acting like an irresponsible teenager while you stay at home holding the baby 
It's just not on!