How long after passing is one able to hear what you are saying to them?

Of course research on this is impossible, so there could never be any scientific answer to it. I would bet, however, that your hubby knew you loved him.
I comfort myself, since loss of my brother, I take JOY, actually, in still writing him the long letters we always wrote one another during our lifetimes, when living in another city. I tell him things I thought about him that day, paste in collages and poems I might have sent to him, tell him about what I saw on a walk that made me think of him. He is certainly with me. As an atheist I don't imagine him anywhere "out there". But as long as I carry our life memories he is alive to me.
I wish you the best and am so sorry for your loss.
Death is simply not always to be predicted, esp. if something happens suddenly. Nurses can judge imminent death with parts of the body mottling and cooling given a slow approach, at least within some days. But a sudden stroke or heart failure cannot be predicted. I would bet your husband felt your comfort and love often in his last days.

Without a doubt. He heard you, and felt your love for him. Without a doubt.
My deepest sympathy on your loss. ((((hugs))))

I can't say if he hears you or not, but several times a month I visit my wife's grave and tell her what's going on in the family, especially with the grandkids, how grateful I was that she chose me to spend her life with, and that I love her. I hope his resting place is close enough that you can do the same.

Whether or not he heard you is I believe irrelevant, as he knew the great care you gave him in his final days and months, and he also knew how much you loved him. I believe his passing while the hospice nurse was still there, was a gift to you, as he didn't want you to be alone when he took his final breath. Now that is true love. May God grant you His comfort and mercy as you now navigate life without your dear husband.

Yes, he heard you. Once the soul passes, he's able to hear everything that is said to him right away, and forever more.

I'm so sorry for your loss. Sending you a hug and a prayer for peace.