[Rockinghorse (Simon)]

Maybe some of you can relate to this problem. My eyepiece case is nearly full. There's space for one more eyepiece and it's calling to me "buy one more..."
Ever get that feeling?
Anyway I'm using a 12" Skyliner Dob and my eyepiece case currently has the following:
Baader Hyperion 24mm (62 and 125X)
Baader Hyperion 13mm (115 and 230X)
Baader Hyperion 24mm (187 and 375X)
Baader Ortho 6mm (250 and 500)
Televue 2x Barlow

So my questions are:
If I get an EP that gives me more than 500X am I ever likely to get conditions when it's usable? Double stars?

Are there any really useful magnifications I'm missing?

If I go lower power with say the Hyperion 31mm that would give me an AFOV around 1.49 degrees which I believe is above the limit of a 1.25" EP in my scope (1.21).

I'm no expert and max FOV's spin my head. Does that mean I'd get vignetting? I imagine the Carina Nebula would be pretty amazing in a widefield low power view.

(Please don't recommend an Ethos! I really like the Hyperions as a great balance of price and quality).

BTW, I like observing everything from Galaxies to planets, though I'm a relative newbie.