A word to the wise - timing belts being rubber, deteriorate with age as well as use/mileage in the same way tyres get hard with age. This is exacerbated by not using the car frequently as the belt will come to rest and stay there. As the natural oils in the rubber aren't circulated within by movement/heat generated by the movement, they tend to dry out and go brittle. This can cause unexpected failure.
Granted timing belts are reinforced but that reinforcement needs the rubber to be in good condition to work. The reinforcement is only as good as the rubber of the timing belt it's bonded within.
Manufacturers specify a time as well as a mileage limit specifically to take this into account. I'd strongly suggest having the belt checked at least once a year between now and your anticipated renewal mileage and if there's any doubt, have it changed. It's much cheaper to have the belt changed than an engine rebuild for bent valves after a stripped or broken timing belt which would have to be replaced at the same time as well.
A recent example for me of rubber going hard with age - i bought my S Type just under a year ago and the front tyres are Pirelli P6000 (as per OE spec), the rears are P7. I have a Vovlo 760 estate i use as a "Dogmobile" which is running on cheap Chinese tyres (surprisingly good and definitely not deserving of the "Ditchfinder" moniker) and took a T junction near me in the Jag during the recent icy weather. The Jag nearly made intimate contact with a telegraph pole on the pavement! 😮
The Volvo on the other hand turned as it should, despite the black ice. Both cars have ~5-6mm tread on the front tyres so it's not that, the difference is the P6000s on the front of the Jag are 10 years old! The fronts on the Volvo are just over 5 years old with the rears being about 18 months - the fronts had previously been on the rear but a pot hole knocked my alignment out and scrubbed the previous set of front tyres out so the rear tyres went on the front and a new pair was fitted to the back.
This prompted an all-round tyre inspection on the Jag and i discovered that not only were the P7s on the back 5 years old but were the wrong speed rating for the car! Naturally i'll be renewing all 4 tyres on the Jag in the near future but it makes you think when old rubber pulls those kind of nasty tricks!