I used to run GNOME/XFce/Firefox/Thunderbird/Python/Gaim/Gimp/Emacs in my computer. That said, what do you think the average download size of
will be if I had to upgrade say once a week and once a month.

Please bear with me as I am a dialup user (unlimited connection at 4 KBps).

I like to know at what frequency (once a X days) if you apt-get dist-upgrade, my download size will be reduced.

(Note: Doing dist-upgrade 4 times in a month downloads more than doing it once in that month)

I would say to do it once a week at least just to save on the one big download you would have to do with once a month. You can also use the -d switch to just download the packages and not unpack and install them. This way you could if it is going to take a very long time to upgrade just let the computer run overnight while you are sleeping then when you wake up and get the time remove the -d from the line run it again, it would then upgrade the packages that were downloaded while you slept plus there would be no interfence with your normal use of the computer.

I would not even consider it as a dial-up user. If you had a shiny new Woody system with no extras it might be worth considering. I had a working Woody system and it was a 600MB download and took 4hrs at 12 times the speed you have. Just buy some sarge disks or ask a mate to download them for you and go that route.