Re: general question regarding all ballistic apps..
As you go farther out, there will be more drop if conditions create higher air density, e.g. low temp, low altitude, but looking at just one .308 load of mine in JBM, the difference in drop between 20F/29.92 Hg and 80F/23.92 Hg is still less than .3" @ 200.
Another reason I like to zero @ 100 is because wind doesn't have as much effect. I try to zero on days when it's blowing less than 5 mph so I'm not saying you won't get some misleading results @ 100 if it's over that. Once zeroed, get out as far as you can.