I've had these boots for a few months now. Probably put 25 miles on them so far all on flat ground. Yesterday I finally took them out on some hills and there was some heel slip. I don't know if it will get better with time or maybe it won't bother me when I get to the mountains. I've read about some people having heel slip issues and different lacing styles. The boots seem good on flat ground but I'm wondering if they'll lock in better as they get more broke in?