Broody? Too hot? Egg bound?

[caralouise1974]

Hmm, she was in the nest for over two hours today, and had an egg under her when I shoo-ed her off. She was a little cross about it, and chirruped forlornly for an hour or so afterwards, but seems to have forgotten again now. She's been chasing bugs and eating layer pellets and drinking lots (and doing a lovely big broody poo) but has not tried to return to the nest.

So how many days might this little game go on for?