OK, you forced me to take a flashlight out in the garage to inspect chain rings.

For the record, I cross chain whenever it happens, without a thought. If I don't hear noise, or run out of gears, it's good. If I hear noise, I adjust DRs, or shift rings..

All of my rings have signs of lube on the sides and face of the teeth, no shiny spots.

This, on semi modern, 9 spds, compact double and triple.

Also, I noticed it's time to get some serious cleaning done! Especially on the Crosstrail.....

The short answer, for me is - on a two ring/six cog set, I will use the small ring with the largest cog and the next three down. When on the big ring, the smallest cog to the fourth one up. Yes there is some duplication there, allowing for the middle range shift to happen. The intent is to minimize the amount of cross chaining.

I'm with wanderer on this one. I use every combination in my 3x10 set up. 2000 kms on the current set up, no significant wear indicated. One should always be aware of terrain and proactively shifting accordingly. Also, I have indicators on my mountain bike. NEVER have bothered to set my eyes on them. I shift into the gear combination that I need for the terrain at hand. So the indicator serves no purpose for me. More important things to look at while riding. Irrevalant and senseless to me.