I (we) had the same concerns. The question you have to ask is "What do I need control of?"
In our operational environment we may require, for example, a quick change to a firewall configuration. Most , if not all, vendors will provide an SLA that provides for such change requests to be implemented within 4 to 48 hours. For most operations getting something changed within 24 hours should be plenty.
If your concern is about response to an attack then you need to have a fast notification time in your SLA. Generally a vendor is going to notify any customer under attack immediately. That roughly translates to within 15 minutes. It's then generally up to the customer to shutdown whatever is under attack.
