The underlayment on concrete tile roofs typically last 20-30 years. This greatly depends on the quality of the material. For instance, most of the track style homes in the valley have a 30# underlayment which lasts 20 to 25 years ( 30# is the thinnest underlayment under concrete tile roofs allowed by roofing code)
So, if your roof is 20 to 30 years old and you have a concrete tile roof then your roof may be leaking already is liable to. Many times a leak can go undetected if it occurs on the eves or gable edges of a roof.
PRO TIP: walk around the edges of your roof and look upwards. If you see water staining, as you can see in this photo, then the underlayment on your tile roof needs to be replaced.
Being proactive instead of reactive with maintaining your tile roof and replacing the underlayment when it goes bad will save you lots of money in the long run (This helps you avoid: Dry wall repairs, repainting water stained ceilings, possible mold removal and not to mention all the other water sensitive items inside your house) Another PRO TIP: walk around the inside of your house room to room and inspect the ceiling for any water stains.