DD went into a big bed at 14months, she started trying to climb out of her cot at 12months and by the time she was 14months had already managed to get/fall out 4 times already :O Funnily enough she was a crappy sleeper as well, once we put her in her big bed......she slept through! Could be a coincidence who knows but it was great! We had rails up for a bit, but she would use them as climbing devices as well so she ended up taking them off.....shes 3 now and only fallen out of bed maybe twice.