I've been battling a very slow leak in two tires on my 2004 Envoy for as long as I've owned it (~ 6 years). One will lose about 5-8psi per week and the other will lose 10-12 per week, so I just make a habit of stopping at the local gas station and checking them about once a week.
This has happened with 2 sets of tires/stems now and multiple removal and remounting cycles. After a removal and remount they'll improve for a month or two, but then go back to leaking.
The rims are in excellent shape, no bends, no curb rash, nothing. The tires have been well cared for and are also in great shape minus normal treadwear.
Any thoughts or suggestions?