Jackdaw in soffits

I'm pretty certain we have jackdaws living in our soffits, and judging by the noise it sounds as if they have a lot of young right now. My question is, how long will this nest remain active? From reading I thought they were meant to leave at the end of the year, but I'm sure the ones living in our soffits have been there for a long time. We are convinced this is their second summer and they never left in the winter. Is that normal?

Obviously we wouldn't go anywhere near an active nest but they are so noisy, when they do move on, we want to fix the soffits. Can anyone help?