Glad it's helpful. I was going to do some kind of journal post on 'easy kindle hacking' but my post pretty much does that =/.
Just had a look - a 1m19sec file (my longest) is 624kb (files are saved as .wav files. So you would need to convert your uni lectures to ogg or mp3 on your computer if you wanted to keep a bunch of them in your kindle, for example.
By my (rough as guts) calculations 1hr = about 30 mb.
EDIT: Thanks Mobad - I want to try Canti, but it fails under wine in Ubuntu. Sorry, I missed your post before. I might try again at some point though because I would love to be able to save larger American style comics with 800 width and read them sideways.