Ha! My first two are 13 months apart and then the third was 18 months behind. I had three under three for five months

Best advice I ever got was "remember there will come a time when they both are crying and you'll only be able to deal with one -the other will have to cry for five minutes.". My second was a very good sleeper though as I NEVER had time to put him down properly. My older would start making noise - I'd go to check on them and the youngest would start - by the time I got back - he'd be asleep. He rolls with everything.
My perspective - with the first you learn how to deal with a baby, with the second you learn how to juggle and schedule - everyone after is easy. It will be tough for the first few years but those years are tough anyway - best thing is they are at the same stage -makes it easy to manage.
Have fun!