My experience is that if oiled (I like mink oil, though some say it's too heavy) any reasonable grade of leather glove, stored indoors, will last at least a decade of occasional use. My Ken Griffey Jr. glove (Wilson? Rawlings? I forget) has lived such a life. I think I bought for around $40 in 2001; I remember it being roughly one tier up from the cheapest glove you could buy. I've admittedly not played a ton of ball with it, but the leather's in great shape, no cracking anywhere... this thing might outlive me unless I get off my butt and join an old man's league every summer.
Recently threw out some gloves I owned as a kid in the 80s. The leather was dry but not cracked; I was tempted to oil them just to see if they could be brought back to life.
What's your experience been?
Not saying you do this, but I think a lot of people store their gloves in their garages or some other place where they bake in the summer and freeze in the winter. That'll kill a glove for sure and while ultra-high-quality leather will surely survive this kind of treatment longer than cheap leather, it's no way to treat a glove of any kind.
I'm sure that inexpensive gloves that see plenty of honest use (2, 3, 4+ practices or games a week) don't live forever either.