String tension and string life expectancy
 

How long would a set of 12-53 last if tuned to D standard on a 25 standard. Assuming you left it there and never changed tunings. A 56 low E up to A would in theory have the same expectancy as a G string since they are the same distance from the breaking tension. How much of difference does D and E standard make in life expectancy of a set of 12's?

If you didn't touch the guitar, I don't think anything will matter. The strings will last a long time in any tuning.

I don't think that tuning to D will make your strings last longer. I think what mostly shortens string life is oxidation and the effect of gunk on the strings to deaden vibrations and cause loss of brilliance. Wiping down strings every time you put a guitar away may have more of an effect than anything else except maybe the use of coated strings.

- Glenn