It is tiring to have them close together, but you adjust just fine, the same as you adjusted to having one from none.
I have 23 mths between my 1st and second and then we tried for 3 mths after having my second, and thank goodness it took that long as we have just 13 mths between num 2 and 3 , which actually is lovely.
The thing to remember is that kids get seriously more expensive as they get older, so for example, in year six of primary school, (age 10) ,we have to pay £350 , via 10 monthly installments before trip, for a lakeside outdoor residential trip, all the kids go, so there is much pressure to send them. Because of my close kids descision, I have now spent the last 4 years, with just one year off this £50 odd a month payment, and it's driving me mad!! I have two months to go for this septembers trip fokr my daughter and I can't wait. Also my swimming lessons cost £78 each child, and they are all needing them at the moment. And again, I think my kids will have to borrow/pay their own way through uni, I could try and help, but can't see that 3 kids close together is going to work, lets hope they don't all get married at once!!!
Having said that, it is lovely to have them together as play mates when little, they really argue now, but that may juts be my kids. I wish Devon could have a freind to play with !