I've had some chains last 600 miles. I average about 2000 give or take with a KMC X10SL silver or titanium coated. I swap between 3 cassettes and do not bother to keep track of each run time. I am riding in dirt, gravel, and wet and I cross chain at times. I do at least wipe and relube just about every ride but I am right back in the dust and dirt soon after. It is what it is and I'm not going through great lengths to squeeze some potential life out of of something easily replaceable and only about $35-40.
The KMC X8.93 is a nice low cost chain for a 6/8 speed. Only 7 speed freewheel I a have used recently is a Shimano "megarange" but I doubt that is what you want.
Last edited by u235; 06-25-20 at 08:29 PM.