"If you try it too early then it leads to weeks/months of accidents, tears, frustration on all sides."
Meh, what a load of old tosh. Started my DD at 10 months, as part of her daily routine. Very happy to sit there and have a story read to her or be sung a song. It's just part of her day, and she communicates to me with grunts and pointing if she needs to go. At 16 months she's fully cooperative, 90% of poos and wees on the potty. She wakes up dry, toddles over to the potty, I put her on, she does her business, and she's off again. She's just a normal toddler. Smart enough to learn to walk, learn to talk, learn to feed herself and yep, smart enough to learn to use a toilet.
My generation were all trained before 2, and it worked. Millions of kids in poor countries can control their bowels by 2, so I'm not sure why kids in the US, the UK and the developed worlds somehow can't...? 'Leaving it late' is a marketing idea dreamed up by Pampers, Huggies and the like to get you lot to buy more plastic nappies. I can't believe that so many people have bought into the mass-marketing lies. You've all fallen for it hook, line and sinker.
Sorry to be stroppy, but this just gets on my goat. I hear it time and time again, that kids can't control their bowels. Load of rubbish.
HTH.