Having bought, and now living on land that had an easement, I feel your pain. My understanding, however, is that an easement agreement must be renewed if the property changes hands; both parties must agree and sign. When you bought, was such a thing discussed with your land-locked neighbor?
If a document doesn't exist, then this could be a good opportunity to put something in place. Besides maintenance, contract renewal, and guest limitations, this is the place to define the amount of liability insurance each party must carry...I'd hate to see you in hot water if some renter injured themselves on your property. And if your property becomes a mudhole and erosion sets in with lots of traffic, it may be on you to maintain it for the other party unless otherwise agreed to.