I've been teaching for 13 years now and I still love it. I'm now in FE, so teach 'A' level and just today had had an email from a former student asking for our help now that she has finished her degree, and now wants to do her teacher training (my subject). When you get things like that, and realise that you really have made a difference in someone's life, then it really is the best job in the world!
I work part time, and so my hours are not necessarily than unfriendly, particularly now my children are at, and reaching school age. I'm lucky in that my bosses are understanding and do let me have time off for nativity and that (as I part timer, I am able to swap my lessons with a colleague) so I don't have to miss too much. I also have most of the same holidays as my DDs and that is a great perk.
As for the long hours, yes I do work very long hours during the week (but I only teach 'A' levels, so marking is very heavy) but I am able to bring my work home and do it when the children are in bed. When they get older, I'll probably stay at work later, so I'll do it before I come home. Because so much of your work is done outside of the classroom, you are at least in control of when and where you do that.
As others have said, if you're doing it because it is a job you love - then really it is the very best job in the world, just don't do it for the holidays, the pay, or the 9-3 hours 