I can sympathize with posts like this one over at Big Bear Butt as I'm a super alt-a-holilc as well. I used to be much worse than I am right now but going into WotLK I made a decision to play no more than two characters. I benched my Druid that had been my main since Vanilla and decided to play my Shaman and my new DK. The group I was running with at the time needed ranged more than melee so I ended up playing my Shaman as my main initially but switched to my DK when the group composition changed and I played him up until TOC when I switched to my Paladin. It was at this point that I made my Druid my main alt again and as I've recounted here on a few occasions I switched back to my Druid recently making my Paladin my main alt. I intend to go into Cataclysm with my Druid as my main and my Paladin as my main alt, but like Big Bear Butt I have a slew of other alts that I play from time to time and even have a few I've created recently to play around with as projects. The character cap has really crimped my style so I've had to delete a couple that I knew I wouldn't be playing again any time soon, but as things go, you never know, I might have wanted to pick back up at some point.
If you were to look at my character selection right now you'd see:
80 Death Knight
2 bank toons (one Alliance and one Horde)
I can empathize with Big Bear Butt when I sometimes play some of my alts and have to recall how to play them, but particularly my Rogue who I really only Battlegrounds with. Even worse is trying to remember button placement as I find myself having to look at my keys quite often when I start playing an alt again after an extended break. But as bad as it seems to be now playing alts, imagine what it was like back in Vanilla and to a lesser extent, in Burning Crusade when I would change characters for long periods of time.
Five years ago in Vanilla I started off playing WoW as a Warlock, but ditched and deleted him at level 24 or 25 when I decided I didn't like it. I rolled a Paladin that similarly I only played until about level 25 before deciding I didn't like it and then rolled a Hunter who I actually played for quite a while. While I leveled him up to 60 I also created a Warrior that I would eventually start raiding with. My Hunter was my first level 60 but I never raided on him which is odd, I know. Back in those days, even after several months playing WoW I still hadn't come to grips with the specific focus of the classes I was playing and never got to the deep understanding that each class really requires to be competitively played. I was a noob and played like one doing absolutely silly things with my Hunter like equipping weapons that in very little way buffed my abilities.
I really liked my Warrior but back in Vanilla if you were a Warrior you were expected to tank, but I hated Prot. It was a pivotal period for me as I would eventually get tired of the constant back and forth with the guild and their expectation that I tank instances and raids and retired my Warrior. It was at this point in the months leading up to Burning Crusade that I created my Druid who hit level 60 before Burning Crusade. It's also what caused my wife and I to server transfer the month before Burning Crusade to the server I still play on today. In Burning Crusade I played my Druid as my main throughout the expansion however I had a slew of alts that I played, including my new Shaman, another Warlock, Mage, Rogue, Hunter, a Priest which I ended up deleted and a few others. I even played my Warrior until the mid 60's before he too finally got deleted. Unlike in Vanilla though most of my alts did get leveled to 70 and I did raid on most of them. But throughout it all I always considered myself a Druid player. It might have taken me a little while to finally create one in Vanilla but once I did I've always felt different about my Druid than about all my other characters.
And I think that speaks to the heart of what Big Bear Butt was talking about. It's the identification to the class and the character that drives that insightful and in-depth knowledge. It's made me delve deeper into the class than I have with any other, not because I feel I need to know more than anyone else (I don't) but because I simply care more about this specific character than I do my others. The first year of WotLK I didn't play my Druid at all but when I finally did dust him off it was like riding a bike. I hadn't forgotten how to play him, though obviously there were some considerable changes from BC to WotLK. Cataclysm will be the same way, yet I know I'll chug along leveling from 80 to 85 without batting and eye.