Collared Dove

We have a collared dove nesting in a yew tree.  They have been there since mid August but we haven’t seen any sign of chicks. Haven’t  seen two birds for some time but one is always sitting on the nest.  I assume they are first time nesters as the nest they built is very precarious. We are worried that they should have moved off by now.  Do we just leave them until they realise they haven’t produced any viable eggs this time round?