Sound deadening is never a bad idea. You have the time so the only other variable is if it works in your budget (if there is one) I've fully gutted and covered cars before to make sure there wouldn't be any unwanted resonance. In my current build I didn't do any yet, I'm going to deaden after the system is done depending on what's left in the budget.
If there aren't any constraints go for it. I never heard someone say the have too much sound deadening.