Some really good comments here made by collegeparent/stanford.......
I am not discounting the natural breakdown of padding from higher level pitching velocity...but much of "mitt life" is definately connected to how it is treated by the player....a well treated glove has a significantly longer life span...
Here is the best advice...(IMO) given to date.....
"He always keep the gloves cleaned and oiled, you never saw puffs of dirt coming out of the glove while he was catching. He never threw the glove, jammed it into a bag, left it on wet grass, dirt etc or touched the ground with it unless blocking. Dirt is like sandpaper to the glove."
wet, sweaty, dirty gloves thrown into a bag and stored in a hot car are going to deterioate fast...
Now to Stanford's excellent comment.......you do get what you pay for...and I am a believer that the gloves of the past were made of superior stuff...I too still have my first catchers mitt...a Nokona Bulldog from the '70s.....and used it to catch my son well into the 2000's...now well retired to my trophy case....
In the Mitt arena, you can buy gloves from $75-$300....and expecting a discount model to last is for years is a poor gamble at best....
In the higher baseball I do, I see a lot of Wilson A2000's and the Rawlings Pro Prefered...and a smattering of Mizuno and All Star...
Try them on, because they fit differently, treat them right...keep them clean, let them dry out after getting sweaty...treat the leather and tend to the laces....and you will get more life....
And if you get one you fall in love with...and "old faithful"...remember that like a pair of really good shoes...they can be rebuilt to like new status.....
Now from my sons time behind the in dish in college...he had a gamer...and a newer backup he used in BP/bullpens....called it his "gamer in training".....