Mileage isn't an issue; these bikes routinely last for 100,000 miles or more.....but the model year is another matter:
early Gen2 bikes had a number of issues, mostly minor including the deep hole issue, wire harness rub through, disintegrating rubber bits and a poor ring design coupled with poor quality control on the cylinder bores which caused many 2008's and 2009's to burn excessive amounts of oil. As I said, most of the problems are minor and inexpensive to fix but the oil burning issue takes a 685 kit to fully address. If you buy the '08 or '09 expect to deal with some or all of these issues.
If it was me, I'd buy the '13 (well actually I'd buy a 2000 - 2007 'cause I prefer them for the offroad centric riding I do, but that's a different issue). ...and despite mileage not being an issue, low mileage is definitely better, all things being equal.