Thread: "You can't teach an old dog new tricks"

As a few of you know from some of my previous posts, I am a novice trainer but looking to get a dog in the next few years to teach to indicate deer for me. My current dog is the family pet, a golden retriever aged 10 (I'll look for a deer dog when he passes). He is quite poorly trained but very well natured so he's never been problematic. In fact, its probably because he's so well natured that we didn't spend lots of time training him well. It was before my hunting days when we got him (I was 8) so he never got any training other than the standard sit, heel and whatnot. I had a thought today that before getting my new dog, I could up my training skills by trying to retrain my dog, mainly on the basics but if he excels then I'll try move him on. I'm not expecting to get a hunting dog out of it, only to teach myself to train in prep for my next dog. Is the old saying true, that you can't teach an old dog new tricks, or is it worth my time - I won't just be trying to draw blood from a stone?