Most tend to get double the mileage from front tires vs rear.
Tire life depends on a lot of factors. What works for one may not work for another.
Type of bike (remember, the "Shadow" name has been used since 1983 on bikes ranging from 125cc to 1100cc, shaft and chain driven), weight (of bike, rider, gear, do you do a lot of 2 up riding), speeds ridden, road conditions (smooth asphalt, rough concrete, dirt roads, potholes, etc), weather (hot temps decrease mileage), driving conditions (lots of start/stops wears tire out faster than steady cruising), maintenance (checking pressure and tire balance), and tire construction (radial, bias ply, tread compound etc).
Oh, and the throttle, brake and downshifting.
While I am not a "speed demon" I do get on it pretty hard getting up to speed many times, and I do chirp the rear tire a lot downshifting without the clutch as well as doing a lot of engine braking.
Was the tire a Dunlop 404? If so, that is the problem. Lots of complaints about them not lasting.
My bike came with 404's on it front and rear. No idea how many miles on the tires (only 7500 miles on bike, but tires were not original, bike is a '94, tires were made in '07). Tread looked decent when I got it. Within 2,000 miles, they were getting smooth.
Shinko tires (777 and 230) are very popular and are OK mileage wise (but are an inexpensive tire), as is the Kenda Kruz.
You will get a lot of opinions, most based on personal use, some on hearsay.
Perilli, Bridgestone, Michelin, Metzler, Continental all have tires that have good reviews, and bad ones as well.
I was leaning to either a Shinko 777 or Perilli MT66 (what I ended up with on the front) when looking for tires, but ended up going darkside instead.
Now I don't worry about mileage.