FBinNY 

Cross chaining is like a high fat desert. Folks make a big deal of it, but it's not so bad if you don't make a steady diet of it.

Any time the chain runs at an angle, friction and wear will increase. But it's a matter of degree. If you look at your chainline, you'll see that cross chain is only slightly worse than so-called OK combinations. However, these days there's a new factor, because the rings are closer together. Many bikes cannot run small/small without the chain brushing against the inside of the outer ring.

So, use the gear combination that makes sense for you. For example if you're climbing a relatively short hill and working through the cassette, the "rules" would dictate that bring the front over somewhere near the middle of the shift sequence. But if you decide that you can climb in on the outer ring with the inner cassette sprockets, this may be preferable to shifting the front mid climb. I do this daily on a particular hill where I work down through the range, topping the hill in big/big.

So, like with your diet, feel free to indulge yourself from time to time, but use some common sense.