Increasing Wear Value

[ChalkLine]

The book tells us the following:

Increasing Wear: After a vehicle has suffered
10 actual breakdowns, its wear value is
increased by 1. A vehicle with a wear value of
10 which suffers its tenth breakdown at that
value is no longer repairable, and is good only
for salvaging parts.
Once the players and the referee are very
familiar with the game mechanics, they may
wish to keep separate track of the wear value
of the components of a vehicle. That is, a
vehicle which suffers repeated engine breakdowns
would end up having a very worn-out
engine but a sound suspension. In this case,
the tenth engine breakdown at wear value 10
would mean the characters need to find a
new engine, not a whole new vehicle. This
rule is not suggested for beginning use; players
and the referee have enough to keep
track of as it is.
If this rule is used, however, the wear value
10 vehicle need not be scrapped upon its
tenth breakdown, as it will undoubtedly fail
only in one or two key systems (engine or
suspension, perhaps). If a vehicle can be
found with a working engine, it could be
transferred to the worn-out vehicle and given
a new lease on life.

However this isn't how it happens in real life. In reality no matter how carefully you look after your vehicle it will wear out if you drive it forever. Some parts are designed with quite short lifespans such as the plastic and rubber elements of suspension. Now, even the mighty Monk of the rulebook making new rubber gaskets out old inner tyres is going to have to admit defeat at some point when the actual struts wear away. This isn't covered in the rules and I think we should come up with some for it.

Essentially it means we're going to have to work out how may hours of use a wear value correlates to. This is going to be sucky as not only does this vary with component it also varies with vehicle type.

So instead of a table or list we're going to need a rough formula that a GM can use to say when the vehicle has advanced another wear level.

My first thoughts is that it might relate to vehicle weight, but here I'm not so sure how to do it or even if that's right.
The second is obviously going to be time used rather than kilometres driven. However this starts to look suspiciously like someone's going to have to keep a log for the vehicles and no one wants to go there. (I have actual clinical OCD and I don't want to go there)

Any thoughts? Is it just too hard and the GM might just make a call occasionally?