I have a 2006 H-D Electra Glide Standard, with 10,500 miles on the original Dunlop tires. In the spring, I expect to replace them. What is the typical mileage I can expect from any tire? The owner's manual says to only use H-D tires. If I replace with the same size tires I am sure I'll be safe, so when the owner's manual says to use only H-D tires, are they doing so to promote sales or is there a safety issue?