Like Allie I grew up in the world where you don't keep the same horse through your riding career. And I still believe that for my students at the barn who want to keep progressing. If they're looking to buy a horse when they first start jumping, their primary needs are something that is very quiet and very experienced. It doesn't need to be very fancy or able to jump too high. But if they continue to progress they will need something that is able to jump higher and quietness is important, but not as big of a priority. Very few people can afford to get a horse that is able to jump big, show successfully at the upper divisions, be quiet enough to teach them to jump, and young enough to jump higher each year.
As far as buying investments go that's a tough question and it probably depends on each person AND the horse. I go into every horse purchase knowing that it's not my horse. My pleasure does not come from owning the horse, but making it. A trainer I know once said, "why do we love training horses? Because we are making art". I thought that was awesome and that's the way I see it. I bought this one pony out of pasture that was basically unbroke. He was also a bit of a maniac.
last summer I went to a huge A show and watched him completely pack his little 7y/o around and win reserve champion against some very fancy competition. THAT was cool. When I sold him I was sad, but no tears. This pony I have now? I really really love him. He's not even on the market but on saturday another trainer at our barn called me up and told me that someone was coming out that afternooon to look at him! I panicked and almost said no. I think when he leaves, there may be a few tears. But when it comes down to it, I want to fill the world with good ponies!
plus, there is always something exciting about horse shopping and starting a new project. At least, that's what I tell myself when the trailer is driving away!