Its not that the airlines are just letting their fleets age, its that if they have tried to make orders for planes, or currently have orders already, its just that Boeing, Embrear, Airbus, etc. are so backed up with orders already, which means they cant deliver orders on time, so it could be years before they would even get half the planes they order. And in that amount of time, what are airlines supposed to do in that time of wait, just ground the plane, even though that it is still flyable? Heck No!
I agree with ect76 alot here! Even if some planes may be 15, 20, 25, etc years old, and may not be as "comfortable" as these newer luxury liners they are building these days, all i care about when i fly is gettin to where i want to go!!! So what if the flight is 2 or 3 hours of uncomfortability, just deal with it and realize that ur only up there for a short time, and not the rest of your life! In regards to the bathroom thing, I dont care if its a lil bit dusty or a little bit dirty, I can always wash my hands after, use some sanitizer, or just take a shower when i land. All i care about is if i have an emergency, there is some place that i relieve myself! LOL
This is just my opinion on the subject
-NAplaya