I replaced my chain this spring, and it only has about 1000 miles on it. My park tool chain checker fits at the .75 mark, but not quite into the 1.0 mark. I checked when I put it on and it didn't fit into either.
It was an SRAM PC 830, which I later discovered that there were better chains. I kept it well oiled and relatively clean, but it seems its almost time to replace it again.
If I do replace it, are there chains that last longer? I was looking at the PC 850 as a heavier chain. I need a 7 speed chain for my trek 7000