We are 100% trained here. Even with Loki's DI (diabetes insipidus) They go outside on leashes, ring a bell or go to the door or I ask them. We go months between accidents, which are my fault (like falling asleep at 7pm and not letting the little one out to poop before bed). But like, i can be upstairs and they will be napping downstairs and wake up from their nap and bark or ring or come and get me to let me know they need to go out outside. I can confidently wait for them to ask, or let them out when I go downstairs when it's convenient for me (so they don't ring 4 seconds after I've just walked back upstairs).
It took a lot of consistency and training and watching them every second when they were puppies. Sneaking off meant possibly peeing. Going outside is still made into a big deal and they get a treat, especially for bad weather (which we have a lot of in Chicago, and no pee pads allowed!). If it's really bad weather, I take them outside (dressed appropriately, umbrella, whatever) and wait for them to go. And I can't just leave them alone all day and expect them to hold it like a big dog. We send them out when they ask or every 3-4 hours or so, depending on their nap schedule. Since I *take* them out and watch them (on flexi's from the porch) I know their schedules and what they do when. It helps to make sure they are empty