You can set the Market to only update apps when its connected to Wi-Fi. If you only ever connect your device to Wi-Fi at home, then this setting could do the trick for you?
Market -> Menu -> Settings -> Update over Wi-Fi only
Update: Bringing in info from the comments by Mr. BusterMr. Buster and Power-InsidePower-Inside:
It seems that the "Update over Wifi only" setting was only added to the Market app in v3.3.11. If your Market app is stuck on an older version then you can try to force an update by clearing the data on the Market app, or manually download and install an updated Market APK, as detailed in this previous questionthis previous question.