Greensleeves- twins are a special case (I don't have twins btw) pre the age of 3 ish because they both need a high level of hands on supervision at the same time. Watching friends trying to round up 3 year old twins running off in different directions an extra pair of hands is the difference between safe or not.
Have you ever tried hand feeding a 7 year old (who can run off) and a 13 month old at the same time? DS2 (4) can fend for himself, but ds1 and ds3 both need me at the same time to do something physical (ie put food in their mouths). I don't have enough hands, literally - if ds1 is in the front room and ds3 is in the kitchen no chance. Having just done lunch I can say that tea time will be heck of a lot easier because my mum will be in so she can chase ds1 around and make him eat whilst I can get ds3 to eat.
I can't understand why anyone would not get an extra pair of hands under those sorts of circumstances- i can't see why your reasons are for doing it all yourself in the sorts of situation we have. When I am at home with all 3 I can't sit an play play doh with any of my children because I have to continually check that ds1 is safe- - so far today I've removed a bottle of cleaning fluid from him, removed him from climbing on the swivel chair, got him down from climbing on the kitchen worktops leaning against the window, and stopped him eating washing powder. And you still think its wring to get an extra pair of hands in? Think you inhabit a parallel universe to be honest where you have the ability to be in 3 places at once. And I had help in this morning. (and also 2 people in to meet ds1 who are going to be working with him, so he was entertained for an hour or so by having more people around).
And before the obvious is asked- I'm oin the computer now because ds1 likes to watch it switch on and switch off and it gives us 5 minutes of non trashing safe peace.
If I had someone in today to help out with us, I would get them to take ds2 and ds3 to the parkor play with them here, whilst I went out with ds1. He's be much happier, ds2 would be happy (loves the park can't go if we have ds1) and ds3 wouldn't be in the playpen for vast hours of the day.
Persdonally I think in my situation its cruel to the kids not to get help in, - especially ds2 and ds3, who without that help will grow up never doing anything because Mummy ewas always too busy with their elder brother.
Mothers of young twins have much the same supervison issues as I have- for a shorter time, and they probably get sensible before they're tall enough to be really dangerous, but for a few years its similar.