Everyone's different, with variable hearing loss, and how the brain/personality can deal with that.
I fly roughly once a month, mostly between UK/Australia and I rarely tell the airline at the booking stage that I'm deaf.
Occasionally, depending on my observations of the activities at the gate, I will let the gate agent know that I can't hear any special/important announcements or if I'm unfamiliar with an airline's procedures.
On board, I usually let the cabin crew know I'm deaf and would like to know the meal choices before we're airborne as it's a bit difficult hear once we're up in the air.
All in all, the less fuss, the better for me personally.