Thinner ropes = shorter life span yes. For alpine use and such, ropes either are used little or they are retired relatively soon. It really depends on your use. For a comparison, simply google "ice climbing rope life". In ice climbing, you are usually using much thinner twins or double ropes. They are usually quite light.
If you are considering being an scenario where a fall could occur, dynamic rope is mandatory. If however you are simply pack hauling or rappeling static is sufficent. The biggest problem is how to control your descent with thin ropes, it becomes very difficult to say the least which requires more gear, perhaps enough to offset the weight advantage of lighter rope. For instance, I have 3/8" amsteel dyneema rope (suitable for ATV winch ropes @ ~ 6000lb tensile strength). The stuff is so light it floats on water, but it's so slick controlling a rappel would be challenging with minimal gear and no standardized belay device is designed for rope that small.
