I agree with you chronoboi001 and Tech.I have all running all the time.Better safe than sorry.I can understand some users that are not on broadband reducing some resources though.Its a case of horses for courses.
Your connection has nothing to do with resources used other than the providers you actually require for the programs you use to provide protection.
I too am a dial-up user and I only use 4 providers, because I don't require the others as I don't use P2P applications (totally out of the question on dial-up), I don't use Instant Messaging (never felt the need) nor do I use MS Outlook, only Outlook Express, so I don't need the Outlook Exchange provider.
I don't notice any impact using either the network or web shields, the network shields resource use is negligible and the web shield's is relatively low, but that is the one doing the most work outside of the standard shield.
So if there are some shields that are specifically for different functions, like P2P or IM and MS Outlook, then if you don't use any of those applications, then you don't need the associated shield (Terminate it).