I'm going to go with manually updating - don't let it try and automatically update.
Company of Heroes has a similar ting in place - without patching to the latest version you cannot create or join games because there are fixes put in that may include balancing out the teams. Similar fixes are prolly in place for NFS:C, but without the latest version, you don't have them which can put you at both a disadvantage OR an advantage depending on what anti-cheating stuff is in place.
Not that you're cheating of course, but if the other guy wants to, it'd be nice to know you're on the latest version and not vulnerable to the stuff available for 1.0 clients
