How long before shoe replacement

I voted 300 but that is pushing it for me (no 250 option).

My shins and knees hurt after about the 200 mile mark and I try to stretch them out to 250. I wear Asics 2160s. 

Depending on how much I run, maybe once a month or every other month. As I have several pairs in my regular rotation it seems like I have a new pair at least once a month. However, my racing shoes can go several years as I only use them for races and have different shoes depending on the race. I stock up on shoes when there are good deals. I recently bought 4 pairs from Running Warehouse for less than $40 each during a clearance sale.

Shoes wear out differently depending on a variety of factors. Type of shoe, weight of runner, running form, terrain, etc., can all play a role. The same shoe that wears out at 200 miles for one person, can last another person more than 500 miles. As such, wear is individual and should be based on your own needs rather than based on the experiences of other people who may not use the shoes exactly in the same manner.

I have been running the Mizuno Wave Inspire 7. Do you think shoes can contribute to Planter Fisciitis?

Just replaced 2 sets of Scott T2C's after roughly 300 miles per pair. 

Looked online at Nike Mayflies, and they print right on the insole that they're only designed to hold up for 100k/62miles!  The initial cost is cheap at $45, but price per mile is pretty high.

Somewhere around 200-300 depending on the shoe for me.  I do rotate 2-3 pairs for training and run-only races (and I have another one I use only for triathlon races).

Those that fall of rotation end up as wear-whenever shoes (though I do keep an old pair in a box in my car just in case).