Hi bb, I can understand your apprehension in talking about end-of-life planning for yourself when your husband counters with “I will follow you.” Might you be able to turn that into planning for both of you? It’s never too soon to talk about best endings and share one’s wishes with loved ones. You could discuss his wishes as well as yours.

Planning best endings is never easy, but it's an invaluable gift to your loved ones. These discussions can be among the richest and most intimate that friends and family share.

This conversation starter kit might help give you some ideas on how to start the conversation.
https://theconversationproject.org/wp-content/uploads/2017/02/ConversationProject-ConvoStarterKit-English.pdf
I think the challenge might be to discuss things constructively. Do you think it might help to talk about him first?