Tyre size's

[Scouse]

Another post concerning tyre's got me thinking earlier. My R6 has an R1 size rear tyre, this I feel makes the bike handle really really well and of course have a kind of tart value in having a slightly fatter rear.
Now obviously I know by riding it that the difference in size makes the bike turn a bit quicker/sharper ie.corners can be done at higher speeds with less lean etc but I was wondering are there any downsides to this difference that I should worry about. I've noticed that the front and rear tyres seem to get to the edges at the same time when cornering which concerns me a little.

Oh and how many miles should I expect out of a BT014r because I've clocked about 600 miles and it doesn't look like there's a lot left on it now seems a bit short lived.