With the right roof sealant, you can extend the lifespan of your roof by years, if not centuries. Sealants do more than just keep water out of your home: they protect the materials of the roof itself, and keep the subframe dry and free of woodrot. The subframe is especially important, because while materials can be replaced panel by panel or tile by tile, damage to the supporting wood of the roof can mean an entire replacement will be necessary in some cases. With the right sealant, however, you can be sure that your entire roof will stay dry on the inside where it counts.
Call a roofing contractor and have your roof inspected for the proper sealant application. If the roofer you call suggests that it is time to re-apply sealant, then it is best to take their advice and have another coat added. A roofer may even be able to recommend a sealant that could improve insulation as well.