A Metzler ME880 wil last about 80% to 90% as long as a Dunlop D401, D402 or D404- because of the softer compound used in it's construction -   BUT- you will feel a tremendous improvement in performance - both dry and in the rain (for bettr traction you'll need to go to tubeless radials) - AND they roll smoother than what you had which you will feel (actually, feel less) in the seat of your pants and in your palms  - AND they will maintain similar fuel efficiency in spite of the softer compound and increase in traction. I suggest you change both at the same time if the bank can handle it.  You will be very happy, especially if you ride fast, ride far or just keep finding roads that make you lean a lot. I've used them (and still do) on larger bikes and they are definitely going on my Savage as soon as I can get it done.
AND, yeah, it takes almost twice as much $$$$ - BUT - your friends (and significant others if applicable) will  wonder what you're smiling about!

I was also amazed!  However I weigh 160 pounds and I ride very easy usually 50mph or less. I  very seldom ride on the freeways and use my bike to commute to work through back roads. I try to ride to get the best gas mileage as possible.