When dealing with extremely low frequency maintenance items like timing belts, you need to think more about the whole lifecycle of your car ownership instead of eeking it out until it's due.
Are you going to do the timing belt once or twice?
Do you see yourself doing it eventually or are you going to sell or get rid of the car before needing to do it?
If you see yourself needing to do it, then you might as do it now for both piece of mind as well as getting use of timing belt2.
Think of it like a pit stop on a race in simple terms (no complex strategies). if the race is 100laps, and you need 1 pit stop. You don't use up the tires for 75laps then put on the 2nd set for only the last 25laps, you split it 50/50 even though tires#1 weren't used up.
If the first timing belt lasted 13 years, the timing belt buys you 13more years (assuming your same usage).
So, if you know for sure you need belt#2, you might as well get it in service sooner and put some use on belt#2.
As a side note:
If the timing belt#2 isn't going to last to the end, then you extend belt#1 a bit more so you can avoid belt#3. If you're getting rid of the car soon, you extend so you don't need belt #2.
All this depends on if it's convenient and if you can schedule other service at the same time to save time and money,
e.g. apply the same logic for the waterpump that's often included in timing belt jobs.
Even if it looks good, and by the book it says inspect water pump; perhaps it's super inexpensive to just have your mechanic change the water pump at the same time rather then inspect, put it all togehter, then have to take it all back apart to replace 1 year down the road.