Onions - Is it too late

Hi All.

Someone at work has given me 3 onions in pots. They had them left over and the stems are around 10 inch high.

I read in a recent post a comment that it is too late to plant onions out. Is this correct for mine or can I leave them in the pots in my porch as they seem happy enough.

Thanks mumofstig. I had a sudden panic as I bet the person who kindly donated that mine would be bigger.