I had 4 with 8 years between the first and last ones. They're all much older now, and you do forget, with time (and loss of memory) how much bloody bloody hard work it is.
I had a DD after my first two DSs and she was a complete dream of a child, very very easy. Thought one more wouldn't make any difference, but my god, it almost finished me off. So much so I managed to persuade my GP and the consultant that I wanted to be sterilised, even though I was only 26. (That was in the good old days - not sure if they do it that young now). But I really felt I had to start taking control of my own life in terms of not getting pregnant just by my husband looking at me, but I was also acutely aware that the more DCs I was having the more my older DSs were missing out (but also gaining in many ways - not that they'd have necessarily agreed at the time, but they have enjoyed being older brothers now)
I'm used to being able to just walk down to the shops by myself now, or organising my weekends around not only what they want to do, but what I want to do now, but it took years and years and years to get to that point.
I have to say, there is nothing better than a houseful of fun and if you can mix in a dog and cat or two, it makes for just about as perfect a family feeling as you can get. There was quite a bit of sibling rivalry we had to monitor and you have to take time to realise each of them has their own very unique personality and although you can't always manage it, to have a bit of time with each of them is a really good thing to do, but that I found those times few and far between.
Now they're all older, the sense of pride I feel when they're all gathered in the same room cannot be matched by anything. They all love being together (for the first hour or so anyway :) ) and I love having them all together.
Go for it, I say and good luck x