I posed a similar question to my first childcare centre, as I wanted 2 days 1 week and 3 days the next. They said no, that the chances of someone else wanting the spare day per fortnight would be slim. Looking at this thread though, I say more families would like a similar arrangement than they think.

At the moment I used a combo of childcare (full day) and occasional care. I just book the occasional care as I need it, they are only open for 2 hours, but it is better than nothing or having to pay for a permanent full day.