Sarah, The best way to know is if you feel ready... However old or young your oldest is you will still wonder if the older one will miss out. It is a normal part of mothering, wanting the best for our children. I have 4 children. The first two were 14 months apart. This was very tiring and I think perhaps a little close, but now they play together and enjoy each other. Then there is a gap of 3 years before two close together again. The gap between the first two and the second two enabled me to get back on top of things, the bigger ones were more able to help out and they were at school during the day so I had some time to spend with just baby. However, you are then out of little baby stuff and have to get used to sleepless nights and nappies and carting the kitchen sink around again. Whichever way you go there are pro's and con's to each, enjoy your kids...they are tiny such a short time.