Brett, I'll switching to syn. this spring in my bird the break in period on my new engine is just about over.

So if I can run my bird on the same oil all summer how often should I change just the filter ?

A side note a few years ago I bought a 89' Buick Lesabre with 172,000 and before I quit shopping Wal-Mart they were the ones who changed my oil.
Only using the bulk oil whatever it was they had I sold that Buick with 315,000 and it still ran like a top.
I was told once that as long as you use whatever oil had the rating the manufactuer recommended you'd be fine.
The oil issue has alot of variables in it conv. oil vs. syn. oil which if I remember right Smokey Yunick was pushing back in the 80's.
Well I bought some syn. oil from a auction last new from a dealer who was going out of bus. so I'll try it this spring.