If you are going to use Amsoil then why not run the Amsoil EA oil filter. Now if you feel the need to change the filter our every 7500 miles then run a Fleetguard Stratapore oil filter. Some like the K&N & Mobile filter but my self I think the Fleetguard has a better oil filter. As for how many miles you can go in between oil changes depends on on many factors so its best to do UOA to see how the oil is holding up in your engine. My self I change my Amsoil once a year as my truck sees very few miles per month do to the high cost if fuel.

 

I wouldnt complain about 60 bucks for 3 galons of Amsoil. I've trying to buy some here in the UK and its over $250 (£130) for 3 gallons of the stuff!

 

If you are using an Amsoil filter and the oil, you should be able to go a lot longer than 7500 miles. I've got 8500 on this batch of 15w40 AME, and Amsoil filter. I am going to do an analysis shortly, to see how its doing, but I have no doubts that I'll be able to go at least 25k miles with maybe one filter change.
Scott