Mine are 21 months apart too - ages, 2 and 4. I am a stay-at-home mum.
My 4yo is all calm and easy-peasy, but my 2yo is a little bundle of energy....however they do play nicely, and do get on well. We have an absolute zero tolerance on fighting (they still do it though, this moring's argument involved Sylvanian Families and smeared chocolate) and I too spend entire chunks of my life tidying up, scrubbing, wiping, disinfecting, only for the house to look just as it did before I bothered!
There is definately no calm in any of our rooms. Every single wall in our house has been smeared or scratched (and then patched up again, to await next time)
I am, however, 29 weeks pregnant with my 3rd, so it can't be that bad or I wouldn't be going for it again!
There are days though when I (making sure the kids are safe) lock myself in the bathroom to weep, but then I feel better for the release. (and guilty for being such a wetbag)
Thing is, being pregnant again means I can't have gin...dammit!
I think toddlers do actually send you a bit mental, but we'll all miss them when they go to school full time!