I have multiple copies of several albums (some entire discographies), and it's for the reasons you've already commented on Paul. Anytime a favourite is remastered - hopefully with the addition of bonus tracks - I'm jumping in like a good little consumer.

I know I'll be missing some, but here goes:
The Beatles discography - original CD's (from 1987) / The Capitol Albums box sets (volume 1 & 2) / The Original Studio Recordings box set (stereo) / The Beatles In Mono box set / The U.S. Albums box set and I still have a half dozen original vinyl LP's framed and hanging in the family room.
The Beach Boys - various CD versions of Pet Sounds and Smile
Electric Light Orchestra discography - originals CD's / remasters / several box sets
Led Zeppelin discography - original CD's / the ongoing deluxe edition remasters
The Monkees - The Monkees / The Birds, The Bees & The Monkees / Head / Instant Replay / Presents (deluxe editions and Rhino Handmade)
The Move - Movements box set / Salvo remasters / Anthology box set
Pink Floyd discography - Shine On box set / Oh By The Way box set / Discovery box set / Piper at the Gates of Dawn box set / DSotM, Wish You Were Here, The Wall Immersion box sets / Th Division Bell 20th anniversary box set
The Pretty Things - original CD's up to Savage Eye / Bouquets From a Cloudy Sky box set
XTC discography - original vinyl LP's (framed) / original CD's / Japanese Paper Sleeve Collection / ongoing Surround Sound series / The Dukes of Stratosphear - 25 O'Clock and Psonic Psunspot + Chips From The Chocolate Fireball (signed by Sir John Johns and The Red Curtain)

I know there's others as well, but these give an idea of my affliction...

Had multiple versions of Who / Faces / Kinks and others...just cleared em out recently and gave them to friends as they were just taking up space.
Same reasons, tantalized by the extras! Had the SF on vinyl and prob. 3 times over on CD too.

Cool collection Mark. I've got some mono/stereo too Painterman. S.F. Sorrow, Kinks, Beach Boys, etc. Here's my Beatles mono/stereo.

Nice piccy Joe.

Yeah I cleared out some unnecessary copies of some stuff but I kept a hold of mono & stereo versions of all my faves where possible. Gotta have Piper, SF Sorrow and Who Sell out in both mixes as they're quite different and both great.

I agree about Piper and S.F. Sorrow. My mono copies are reissues, but i'm just glad to have them and they were affordable that way. Great in mono.