A few years ago I noticed that some trim on my house had water damage which meant that my tile roof wasn't working correctly. I called three roofers (one of them has a Saturday morning AM radio show). Two said that the tile had to be removed and the underlayment replaced and then the tiles put back on. Porter came out and said that the valley that was originally installed wasn't up to the task of our infrequent but heavy rains. He suggested re-doing the valley and that's what we did. Problem solved.
Last year I noticed some discoloring on my kitchen ceiling (uh-oh!). I called one other roofer and Porter. The other roofer said he'd have to remove the tiles, replace the underlayment and re-install the tiles. Porter said the flashing around a skylight was the problem and should be re-done. A crew came out within a few days and fixed that problem but noticed another problem while they were up there and just went ahead and fixed it - no charge.
My roof is eventually going to be replaced. I won't even bother getting other bids.