I got less than 11,000km (6800 miles) from the BT021's front and back. Mostly riden in hot climate 28-36c (83-97F). Always 290/290kPa (42/42psi).
Front wore out the edges and left the centre with plenty of tread (dual compound). One short ride on on twisties did what I estimate to be 80% of the damage to the front. It was a 40C (104F) day but dash temperature was 42c on several occasions. I washed the bike on the weekend before this ride and noted "front is good but I'm up for a rear". On the hard braking downhill section of the above ride, I thought I was getting a flat front tyre so backed right off. It was very squirmy through the corners. I called in at the next service station, checked pressure as about 305kPA, which is normal when hot, and saw that there was no wear left on the outside of the front. It wasn't "belted" but there was no tread left in some parts. I suspect that heat is not this tyres friend. Heavy bike, hot day, hard braking into and through downhill corners may have been too much for it.
I did a hard braking test coming into my garage later. The tyre pattern left on the floor shows the front tyre does flatten out a lot. This, rather than my cornering prowess, probably had a lot to do with the wear. When flattened, the softer outer would be copping a hammering and has left the hard centre comparitivley good. A bit more pressure in the front might have been benificial.
The rear just wore progressively in the centre. Nothing unusual for the majority of the riding I do down the highway.
Back to the BT020F's for me.