My understanding is that UV tends to accelerate the aging process. If the car has been garaged, then you could probably get away with extending beyond 10 years.
FWIW, in 2015, I had tyres on my 180B SSS that had a 3-digit code (2 for week, 1 for decade), ending in 0, so could have been more than 30 years old, but still worked fine. I did replaced them very quickly, though, once I discovered what the code meant!