we have 6 sets (BR, DR, LR, my office, Mrs. office, studio) of exterior double doors, and another 3 single exterior doors (master bath, laundry, studio)....that's a lot of exterior doors to maintain.
replaced the worst 3 with steel doors this year, rehabbing other wood doors to buy another few years before replacing them too with steel doors in later years. except for the front doors, all the doors are full light doors. lets a lot of sunshine in.