I am a mechanic and I have told a lot of people, I DON'T CARE WHAT THE MANUAL SAYS, DO IT AT 60000 MILES.
Its cheaper to do a Timing belt, even on a Jap car, then it is to replace the heads or engine. One customer towed his 944 to me and I said you have 98000 miles and never did a timing belt, his answer was I thought I could make it to 100000 miles. So close, but not close enough, it not only bent the valves in the head but cracked 2 of the pistions. It needed a whole NEW motor.
So many break downs are because people don't do basic stuff, like fuel filter at 10-30K miles, or trans service, etc....
Pay a little now, save a lot later. Its up to you, I will get paid either way, it just depends how much.