I bought my (now 32 yr old) Capri laser in 1992 so have owned it 25 years and passed the half life ages ago. It was probably still my daily then!
What I think about is the mileage, and if I'll ever get chance to wear it out.
I probably put 2-3000 on it per year, 30k currently on it's mildly tweaked 2.1, so another 10-15 years before it's on 60k, when it reaches 90k I'll be well and truly retired, and wonder if I'll still be alive to push it to 120k......
I therefore surely need to drive it more. (I have just done London-Manchester and back in it this weekend so am working on that)
The current tyres will perish before they are worn out.