Everybody has a trimming schedule that works for them. I am approaching the 13 month mark right now with no trims. I've tried to S&D several times; I sat by my window and sectioned my hair and looked through the length. After about 30 minutes I give up since I can't find any split ends. In my entire life, I have only found one split end, and that was when I occasionally flat ironed and washed my hair daily with a SLS shampoo (and no condiitoner). I probably had a few more, since I didn't examine my hair as diligently, but none of my friends managed to find splits back then either. I have a solid 1/2 a month growth rate, and have managed to keep every inch. When I take my hair down, the bottom still has the same layered shape from when I last got it cut. In fact, if it wasn't for the fact that my front, face-framing pieces are grown out, my hair would look pretty much like my very first cut at a salon that does the "deva cut". My last cut was at the salon but a shorter version. So, in over a year of no trimming, my hair has no splits, no damage, and has managed to retain the same layered shape, without adding any noticeable taper. Considering it is still fairly short, some people may not be very impressed, however this just goes to show that not everybody needs to trim several times a year. In fact, I have never had my hair trimmed. I always go to get it cut, and never get less than 4 inches taken off.
So, to the OP, you should do whatever you feel comfortable with. If you have never gone this long without a trim, I suggest you use discretion. If you find that your hair is starting to split more, and that the splits are traveling, get it trimmed. It really would be a shame that after a year, you have to trim back to where you started. I wish you luck.