I am late to the party and I am sure someone gave you my answer but here goes anyway. If you are thinking of selling your property and though the roof is not causing you any problems, most buyers hire home inspectors to review the house prior to closing. There is a good chance the inspector will advise the buyer that the roof is in the last years of it's expected life and it will need replacing sometime soon. The buyer will request that it be replaced or they will request a credit at closing. This probably will occur even if the agreed upon price is a good value. In this market, buyers are expecting a turn-key home in newer condition so I suggest that you replace the roof now so that when you place it on the market, you have stronger offers and a less stressful transaction.