My trainer and mom tell me to ride her as much as I do. They even say I need to ride more. I trained her over the summer to be ridden (my trainer told me what to do and supervised what I did with her). She's trained horses for over 40 years and my mom rode every day all day until she got married and had kids. I don't abuse her or anything. The only long ride we've ever gone on is 5 miles one day, 14 mile round trip the next for charity, and a few more the next day on trails with the people who held the charity ride. And I'm only around 90 pounds I wouldn't even be on her if I was heavy. I'm not even fully grown myself yet.
If you say she can't be conditioned then I'll just try to ride another horse.
And it's not that she's not trained. She's green, sure, but even over the summer with only 2 months of training under saddle she was better than a handful of horses at the 4H fair. My mentor (trainer) told me I'd have my hands full with her next spring, though. Trust me, I love her to death and she's my pride at joy.
And Eolith, I can't read your link thoroughly right now because I'm about to leave school (I'm on a school computer), but I don't ride Lily like a racehorse. We never even canter. I have on her before, but we just walk and trot 99.9% of the time. At least this last year we did. I know that's probably no excuse. I'm just following orders.