I've been a long-time Gel 1000-series runner (over a decade!), in the last few years averaging over 400 miles between changes.
In Nov-11 I moved from my second pair of 1150s (about 420 miles to each pair - I record all my runs with a Garmin) to a pair of 1160s - it took about 90 miles of running before I got the unmistakable signs of worn-out shoes (Achilles tendon tenderness is the first thing that usually happens for me - I think due to over-stretch once the cushioning in the shoe's heel wears out); ill-advisedly, I completed that particular week's schedule in the shoes (I had trouble believing they had actually worn out) and it's taken 10 days for the symptoms to subside.
This topic is a few months old now, so I'd be really interested to hear if anyone else has noticed a severe degradation in the lifespan of their Gel 1160 shoes compared to previous models. I've had a couple of pairs of pretty much every 1000-series iteration with no problems except for the (I think) Gel 1110, which I vaguely remember as unsuitable for some reason.
BACKGROUND: I will typically run an average of 30 miles on-road per week; my weight is essentially stable; I have tried other makes & models (off the back of various gait analysis sessions over the years) for moderate over-pronation, but never been able to get along with them (including Gel 2120s a few years ago, and Mizuno Wave Rider 12 (?) in 2010), typically resulting in shin splints & achey knees in very short order.