I'm sure I have frames that are 40 years old. What do you mean by "on their last leg"? They can be repaired. The "last leg" to me would be when some wax moths have chewed so far through the wood that it is falling apart.
I have had more issues with rodents than wax moths but I did have an infestation of moths last summer that was a pain to clean up and did do some damage. I have a frame that has the point on the edge of an endbar and about have way through the top bar that was gnawed by rodents. That said wooden ware is cheap if you make it yourself out of rough cut lumber from the local sawmill.
My wife's fe-lion regularly brings rodents in the dog door and leaves guts in our house but the other day when I was cleaning up hives that didn't survive the winter the cat let some mice get away. A lady I work with is on the board of the Humane Society where we got the cat. Last summer I set her a mail message saying we wanted our money back because the cat brought in a chipmunk and let it go in our living room. I said that usually she would just leave guts on the floor and it wasn't exactly what we wanted but it was workable. Bringing in rodents and letting them go was unacceptable. The response I got was "You don't need your money back... You need another cat. Clearly that one is overworked!" Maybe I need another cat. Before I was married I saw a mouse in my house and put out glue traps. I caught 7 the next night. Maybe I should put glue traps around my hives. The only problem with that was after my wive moved in and brought her cat all the sudden the cat stuck its paw under the refrigerator, got it stuck on a glue trap and pulled it out with breakfast on a platter. The last thing I want is a cat stuck on a glue trap.
I have the added issue of ants chewing through hive bodies. I need to fix that with a water barrier around my hive stands. Maybe I could build a beehouse and use AZ hives and put ant/rodent traps in the beehouse around the hives where the cat can't get them. Might also make it nicer to work with the bees in the shade. I just can't seem to find any AZ hive plans that I understand. I think I actually need to see one to figure it out. The pictures online don't make sense.