My personal workflow is this: Incoming mail goes to my Inbox. It stays in the Inbox until I am done with it. When I am done with a message, I archive it. I don't choose different archive folders for different messages because I find that the global message search provided by both Thunderbird 3 and Apple Mail (via Spotlight) is much better for retrieving old messages.

I like to keep the archive in the same account as the Inbox, however: This way, when processing work messages from home I can find the archived messages from work, too. And vice versa.

The subdivision of the Archives folder by year is done for two reasons: First of all, I feel it might avoid performance issues caused by folders containing lots of messages. Secondly, Thunderbird does it like this and I use different computers, not all of them Macs, so it seemed to make sense to be compatible.

For me, the main appeal of the A key in Thunderbird is: after being done with a message, I don't need to think about where it should go, I just hit A. In the same manner, I hit Command-Shift-9 in Apple Mail. After having tried this for a while, I found out that the cognitive overhead of thinking about which folder a message should go to was larger than I thought, and I felt a huge relief after I realized I don't have to think about that anymore.

Dragging and dropping messages is out of the question for me -- I am a keyboard junkie.

Perhaps that explains the motivation behind it. I realize that different people have different habits. My habit is not catered for by Apple Mail, so I wanted to change it. I thought maybe there are a few readers that also know Thunderbird and that also like the A key and miss it :-)