I want to get the Horse Armor but I don't want to use it on Shadowmere since she can vanish forever because of the bug it can cause. So where is the best place to "park" Shadowmere for very very long durations, to were I can always go back and get her at a later date?

Thanks

Park her right where you first found her. If she gets lost/confused or if you get on another horse, that is where she goes anyway.

(I don't use horse armor, so I don't know/care about that glitch you mentioned.)

Since she is essential(unless you modded it to allow her to be killed), using horse armor on her is (almost) pointless.

I wasn't going to use the horse armor on her, that's why I need to park her for a while so I can use the horse armor on a different horse and when I want to go back to using Shadowmere again then I'll be able to track her down.

To Acadian, I don't remember where I got her. Wherever she and I were when she was given to me as part of the Dark Brotherhood I guess. (Fort Farragut?)
I did loose her once were I was by a magic well and got attacked by ogre's and during battle she just ran off. She never went back to Fort Farragut so I thought she was gone forever, but 3 months later (real time, not game time) she showed up stabled outside of Skingrad. I was so happy . I don't wont to loose her again so any ideas of where to park her would be great!

Yes. Fort Faragut. Park her there.

Yea, keep here in Fort Faragut, where Lucien Lechance lives/lived.

She never dies so you don't really need the horse armor. That being said park her at fort farragut or at a stable.

I know but I like how the armor looks so I wanted to try it out, I don't fast travel a lot because Oblivion world is so amazing looking, so 70% of my traveling is by horse and it would be cool to see the armor.

Fort Farragut it is then, thanks guys!

If you want to use her when traveling and not lose her just park her in the nearest stable make sure the gates are closed and then run to your destination. Ya that's why I rarely fast travel half the fun of oblivion is seeing how amazing the world looks.