I just did my first 6-month interval, 5500 miles. (Normally I do about 4800 mi. in that time, but this August I bugged out to Alabama for Gustav.) The GM OLM was reporting I still had 33% oil life left.
PP 5w30 is in the crankcase until April 10 or thereabouts. I may go back to conventional, or a syn-blend. My local AutoZone has 5 qts. of Valvoline Durablend and a Fram Tough Guard filter combo on sale for $17.99. That sort of sale, plus the $10 my regular mechanic charges to change my oil if I bring the supplies, would keep my oil changes under $30, less than $60 for a year.
If I go ahead and buy jackstands, I could do it myself (though I might be risking some neck strain), and then I could go with Formula Shell from Target at $2.29/qt. and a $4 filter. That would get me to $30 for the whole year.
Understand, I made these same kinds of calculations when the economy was (apparently) in great shape, not just now when everything is so shaky. I've always watched gas mileage and maintenance costs.