Of course you can stick with the version of the apps you've got if you don't want the newer version for whatever reason.
I often wait a short while before updating, as sometimes the developer will release the new app without the checks they should have done and there'll be bugs, etc. I wish there was an easy way to roll-back to a previous version (without doing a phone backup and restore that seems a bit excessive for a single app upgrade).
With some apps though, it does make sense to update. Sometimes they will have removed a security flaw, or an issue that could potentially cause the app or even your phone to crash/hang/go slow.
YMMV
You can roll-back to a previous version. Just go to manage apps and uninstall latest update. I did it with maps the other day because the updated version was horrible.