If you put 6000 miles on the stock BT0 15's you are pretty gentle on tires. The BTO 15 is a good tire and has been replaced by the BTO 16 and now the latest version the S20. So you have better choices if you choose Bridgestone.
Here is my view on tires:
When you buy tires that give more mileage, you get less grip. That's just the way it is in the world of motorcycle tires and there is no exceptions. Since the front tire is the control point of the bike I am reluctant to install a high mileage touring tire up front. You may say "I don't ride the twisties nor do track days so why should I need a sticky tire up front"? My response is "If I have to throw that beast on it's lips in order to miss a car, deer, etc. etc. or if a vehicle pulls out or turns in front of me and I have to brake hard enough to lift the rear tire I want that puppy to stick.
On my busa I run a Performance tire up front and a touring tire on the rear. Right now it has a Dunlop Q2 front and a Roadsmart rear. Great combination that has good tire life and gives me confidence that the bike will behave properly. Many on this forum do the same Sport/Front Touring/Rear. I have also run a Bridgestone BTO 16 front and BTO 23 rear which I liked as well. If you choose this combination I'd suggest staying with the same manufacturer for both tires. Don't buy a Dunlop Q2 front and a Michelin Pilot Road III rear. Both front and rear tires should be from the same manufacturer.
Just a little food for thought when making your choice of tires.
