How do archive all messages over 5yrs old for easy access if needed

Question

My Thunderbird folders are very large after 10 years and I have over 100 sub-folders. I need to keep all messages but would like to keep the oldest, say over 5 years old, separate as I rarely need to see them again. Archiving would make navigation easier. Where in Thunderbird's help pages does it explain how to do this , as well as how to access the archive ? Is it better to make a new profile called Archive and move the archived messages to that ?

Answer 1

Assuming you have all your emails pre-organised in folders called : Acme, Brown, Carter etc
When you created the Archive options, if you had selected yearly and retain folder structure, then it would be archived as follows:
> Archives
> > 2008
> > > > Acme
> > > > Brown
> > > > Carter
> > 2009
> > > > Acme
> > > > Brown
> > > > Carter
If you selected monthly and retain folder structure:
> Archives
> > 2008
> > > >2008-01
> > > > > >Acme
> > > > > >Brown
> > > > > >Carter
This would mean that all the Acme, Brown, Carter folders would be in Archives, but the size of the folder will be smaller because it is divided by year, or even smaller if monthly is used. (If you only have a few emails per month then yearly would be ok). So, if you have not organised your emails into eg: Acme, Brown, Carter folders, then do this first, then when you Archive them they will still be located under Archives in a folder of that name, so easy to locate.
Folders containing emails that you see in the Folder Pane are in reality mbox files - not folders, and these files are stored in your profile folder.
Each file has emails stored one after the other, in the order they were downloaded, so emails are not stored in individual files. If you accessed your Profile folder and opened one of these mbox files using 'Notepad', you would see one huge long document. Each mbox file also has a .msf indexing file.
Large documents carry a greater risk, if something goes wrong, you could lose a lot of emails. The point of using the auto archiving is that this will sub divide those large files into smaller files and therefore carry less overall risk per file and use less memory when accessing.
http://kb.mozillazine.org/Performance_-_Thunderbird
'' Thunderbird loads a folder's *.msf file into memory whenever it opens the folder. By default it keeps up to 30 *.msf files open for 5 minutes (and their contents in memory), unless they are "special" folders, which it never closes. It loads the inbox.msf file for every account on startup. The best way to minimize the amount of memory used is to archive messages you have already read or otherwise no longer need in Inbox into folders that you rarely open. Moving a message to an archive folder opens it, so consider archiving messages by year and month rather than yearly so that the archive being used doesn't get excessively large. ''
If you choose to not use Archive options and instead manually created Acme, Brown, Carter folders in the Archives folder,it means you will have to manually move emails into those folders.
In which case, you will just be creating new large folders, which will get larger everytime you move an email. As they are Archive folders then they will end up with even more emails than you currently have, so I'm sure you can imagine what could happen over time. With Archived emails you need to consider the long term.
At the end of the day the choice is yours, but at least you now have some information to make an informed choice.