I appreciate that this isn't a Saucony question, but hope you don't mind us offering an answer.
Wear on the inside of the heel is often due to the foot rotating inside the shoes (and rubbing through the fabric at the point with the greatest friction – often the nobbly part of the heel/calcaneus). This can be down to poor fit (sometimes remedied by lacing) or possibly the shoe being too-supportive under the arch which in turn encourages the foot to move without the shoe.
Overall, somewhere between 350 and 600 miles is about accepted for the life of a shoe, but you might want someone more independent than me to back that up! The range is so wide because of the impact gait, running surface and suitability will play on the lifespan.
Also, for those looking at the outsole of their shoes as a guide to how much life left, remember that the outsole is generally carbon rubber and is just about the hardest-wearing component in the shoe. IT's the white midsole that will compress and deteriorate first. Keep an eye on that for creases and the feeling of "flatness" when running, particularly on hard ground.
This is a question that comes up every now and then. Just for your information, I've checked with our production guys and all Saucony technical running shoes are vegan friendly (other than our walking/fitness type shoes with the advertised "Leather upper", of course!).