Exactly the same Annobel! I found that I was flat-out with two, so another one in the pot wouldn't make a whole heap of difference. Ditto with number 4. With 3 I found that the oldest two would play together and no 3 would nap so I'd have 2 hours every afternoon to chill. Never expected that.
You just have to make sure you fill that time wisely! And NOT on laundry!