Why do it if you don't know if it will work

So, I'm not dumb enough to believe that just because I take my child to the potty when I hear him grunt- that makes him "potty trained". My theory is that he wasn't potty trained, but he had US (his parents) potty trained. We heard/ hear him grunt, we dropped/ drop everything to get him to the right place.

He's 15.5 months now, and he's finally communicating to us his need in another way besides us noticing our little grunt-meister doing his buisness. He actually signs it now- or has been for a week or two. We are thrilled. Wasn't expecting THAT for a LONG time - until about 2.5 years.

So, why would we continue all this time, (7 months) if we weren't sure it would get him to potty train any younger? Well, lots of reasons.
1. It's just cleaner.- A poopy in the potty, or even a half-and-half (half diaper, half potty) diaper is easier to clean up after than a poopy diaper. I work 3 days, so we have a nanny, she'd prefer to take him too. It's just more pleasant.
2. Diaper rash-I have really sensitive skin and so does my husband, but our son has had almost NO diaper rash. The exception is when he happened to have diarrhea and so we couldn't always catch it. Diaper rash happens when poop comes in contact with pee for any period of time. Parents who are trained to listen for "the grunt" generally know immediately when their kid has done the deed. So if we make it to the potty on time, then he has almost no exposure to the poop. If we don't make it on time, then we are still much more aware than normal parents. We haven't trained ourselves to ignore the grunt.
3. Peace of mind- I just didn't feel right about teaching my kid to poop in his pants for 2.0 years or so and then "ripping the diapey out from under him." As a parent, you gotta do what makes sense to you. This is just what made sense to me.