I can give you both sides...
I got pregnant with Jesse (#2) when Kirsty (#1) was 6 months old so there is only 15 months between them, it took about 14 months to get pregnant with kirsty so that was another reason we tried earlier as we thought it would take a while again but i caught 1st time. People said it was going to be hard, especially if kirsty wasn't walking, i'd be heavily pregnant and still have to carry her,i guess i was lucky as she started walking by 10 1/4 months

, it wasn't as hard as i thought it would be from what people said, i think with a first baby you adapt around them but with any other babies they HAVE to adapt to your way. They are very close with each other and sometimes you'd think they were twins but they also fight like cat and dog but thats kids i guess. Potty training seemed to last for ages cause it was one and then the other and nappies seemed a normal part of my life, i couldn't remember life without nappies and wetwipes lol.
Had Ben (#3) when Kirsty was 7 and Jesse was 6, Kirsty was a gr8 but Jesse was unsure how to take to the baby, wouldn't hold him till he was about 2/3 wks old, now he is a godsend, they get on so well it makes me so happy watching them together.
When Ben was 20 months i got pregnant with Becky (#4), i knew i wanted a 4th but i enjoyed the one on one time with Ben so much, i did feel i missed out on this with the Kirsty & Jesse, i couldn't imagine it not being just 'us' anymore, anyway Becky is here now and ben was exactly like Jesse was when Ben was born, he didn't want to hold her or anything at first but has soon come around, now he goes up to her and kisses and cuddles her its lovely.
I do feel i missed out a bit on that one to one as the 1st two were close together, but also as they were so close they didn't wish the other one to grow up so fast so they could play together like my bigger 2 did when Ben as born, because he couldn't play, walk, talk, run etc they soon didn't bother with him untill he started crawling etc, thats more so when they started to interact with him.
At the end of the day, its your decision, you have the hard work, have to carry the baby etc and its your body it'll be taking its toll on.
Do what you feel is right and don't let anybody tell you otherwise.