I am in your boat. I found the first six months very hard, and at 11mo dd is now just sleeping through. I was routine-based with her, and she formula fed, which meant dh could step in at any point. This saved my sanity.
He wants another, im indifferent. We have concluded that we will TTC once dd starts preschool at 3.5. This means that any future dcs will be born once she is in full time school at 4/5. I was a little concerned about the age gap, but there is seven years between me and my dsis and I can't think of any megatives about it when I look back on my own childhood.
Lots of people say to me "get them.both out of the way together" but two lots of nappies and two lots of bottles and two lots of night wakings would kill me. I work.full time too, and my DM is a CM and minds dd when we are both at work (I do shiftwork so works out at 2.5 days with her), and I force.money onto her as it is her job, so I would feel guilty asking her to mind two of my dcs at the same time and twice the cost would cripple us.
At the end of the day, you can only do what is best for your little family, and if having a five year plus age gap is best, then dont think.on it. The only concern would be age. Im 27, dd nearly one, so will be 30/31 when I next ttc which for many is when they start ttc their first.