"Because there are a lot of stupid update checkers"
Really you were worried about the 12 packets that java would send to check an update once a week? Or worse case when you launched the program. Firefox for example does not check for update in the background, to be honest not too many use any sort of service or other application running to check. Java for example does -- just turn that off if you worried about the 2Kbtes
You do understand that 1 ad you load on some website is prob more traffic then every single program you have on your box checking for update.
If you were worried about update checking -- turn off them in the program, disable the background service that might be running. If anything the ones that would be causing traffic, minor that it is in the background would be things like dropbox and evernote, etc. But again those are Running in your foreground, not in the background if you don't wan tthem using bandwidth, like I said don't run them
What you should do is fire up wireshark, and then close all the programs your not using like dropbox, evernote, etc. And then just see how much traffic there is -- there shouldn't be any is my point! Your box should not be talking to the internet when your not doing something. Except for say windows update -- that is once a day.. And even other things that might update, they are going to be on some daily or weekly/monthly schedule -- not hourly or anything.
Glad you got on your wifi, but you were looking in the wrong direction for bandwidth savings