Twins?!

Before our first son was born I always thought how great it would be to have twins (a boy and a girl) and then be done with baby making.  I'd have my boy and my girl and be able to go through the whole thing at once.  Now I have two boys but they're 15 months apart.  When I think back to my earlier thoughts of wanting twins I just shake my head and laugh about how little I knew of the challenges of raising one, let alone two at the same time!  It's funny, now I hear my friends with no kids making the same argument I had at that time and I just sort of laugh.

Do you have twins?  Is it as impossible as I imagine or do you think it's easier having them progress through the Stages of Life simultaneously?