I concur with what AV8 has written, but would like to add a caveat: don't count on ATC to initiate a search if contact is lost. True, if the loss of contact is "unexpected", action will be taken. But in reality, controllers routinely lose contact with VFRs - especially en route controllers - and don't consider it to be "unexpected".
In other words, a guy wanders off radar and communication and the controller files away the strip (if there was one) and that's that. Happens all the time. Flight plans are good for search-and-rescue, flight following is good for traffic advisories and safety alerts.