I don't have a lot of alts compared to some people. I have Elionene who was my first high level character, and then I made Salthier to level with Lal and we got them to level 80 first. I started a character of every class to try them out, but left most of them dwindling on odd servers around level 10. I do have my future Shaman healer up to 50 now, and my bank alt, Frelon, languishes at level 15 while doing the economic bidding of my other characters. That's a total of four toons I log on regularly.
Compare that to other people in my guild with dozens of toons above level 50 and 60 spread across multiple servers, accounts and factions.
However, even with a limited number of alts, they have different professions, banks, gear, etc. that I sometimes need access to and need to mail around or "alt hop" to find what I need at any given time. Often I get asked if I can make a LW pattern while on Salthier, of if I can do a flask on Elionene. Having to alt hop just to check these can get tiresome.
Enter Altoholic from Thaoky.
Altoholic keeps a record of each of your toon's professions, the contents of their bags, their banks, their guild banks, their gear, their quests, and a few other things. I can't tell you how incredibly useful this is. By opening up Altoholic you can browse basically any information on any of your characters while on any of your characters. You can also search your inventory or recipes to see if you have a certain one, and link them to chat from the Altoholic window.
In addition, if any of your guild mates have altoholic or show you their professions through linking it in chat, Althoholic will store that information so you can look up other people and what they can make. There's also a section for looking at achievements, and tracking how much time you spend on each of your characters.
It's a lot of information. I find it most useful for looking up quests, recipes, or items that I might have on other characters but that I need on my current characters. Or just to check my current guild bank without actually having to go to the guild bank. I do this on my Shaman alt who is in my vanity guild to see if there's anything in there useful for her leveling.
So I highly reccomend this addon for anyone with a ton of characters, or even just a few. It's a great tool that can prevent having to hop around from alt to alt too much.