See but she hasn't earned the right. Her age may have gotten her half there but when she refuses to stand still for mounting and rears/back up when I try to "force" her to stand still, I'm not just going to be like "whatever, you're old, do whatever you want."
I'm sure my opinion is different than many, many others but I have learned that EVERY horse has earned the right. You will get much farther with her picking your battles, giving her the benefit of the doubt with every new day. So what if she does not stand still for mounting? But IF this bothers you so much I guess.. If you "Hold her back" to make her stand your being counter productive. If your set on starting the argument so early with her by requiring she be still for mounting make that THE GOAL for the day. When you put your foot in the stirrup and she goes to move, quickly remove your foot and make her move, move, move, move! Do not try to hold her, she'll likely back up, rear up or otherwise argue. If she moves when your foot goes in the stirrup you get 10 feet taller, waive your arm, ask her to move away from you and yell "move your feet! You wanted to move, MOVE" Send her away, do a few quick circles, then your done. Clean slate, try again. You may have to do this 27 times getting only a little farther in the saddle each time, once your in and she hasn't moved your done for the day.
It sounds like your asking a bit much of her. If you know she's lived as a pasture puff for 20 years you should know she's beyond the point of caring to learn :) Once again, SHE HAS NOTHING TO PROVE TO YOU... But you... Have everything to prove to HER.
I get SO many horses in from people who flex, bend, correct leads, don't do this, trot like this, set your head like this, every ride is a lesson, a work out, a drill and so fourth saying the horses haven't earned the right to enjoy riding yet 'this stupid horse doesn't know everything and dosent pick up the correct lead every time' it just makes for angry problem children.
I guess we'll have to agree to disagree. =) I personally think that I should be able to enjoy riding her instead of having to leap on to her back like some sort of monkey because she's going to start moving when she feels me getting into the saddle.
I know that holding her still is counter productive, that's why I'm not holding her still. I used to try to hold her still when I first got her and that didn't work, so I stopped. I've also tried the whole making her work when she moves deal but that also doesn't work. So now I'm trying flexing (which is actually working btw). Eventually I'll probably give up (unless we fix it/make it better first) but I'm not willing to yet. I don't think there's anything wrong with having expectations for her, especially very simple ones. If I were expecting her to learn her leads or flying lead changes or something and being all mad because she was't figuring them out, sure she could be beyond that, but standing for mounting is a very small goal.
And see, she's not beyond the point of caring to learn. She wants to learn. She loves working with me, she meets me at the gate and stands wanting me to come back when I leave. She soaks up everything I try to teach her, as long as I'm teaching her in a way she understands. She's learned 5 new words and the actions that go with those words in the last 6 months, that doesn't sound like a horse that's beyond wanting to learn. She learned to "stay" in less than ten minutes using some grain and lots of "Good girl!"
Her age is just a number, not a death sentence. She has every right to have the benefit of the kind of training any young horse should get. I say she deserves that because of her age. She deserves to have me enjoy riding her and that starts with standing for mounting, beyond that I don't really care. She's a great ride and I love riding her, just I don't like the whole circus-like mounting shenanigans.