Look up some forums and figure out the expected maint. costs annually. That's the best way to tell and take the bias out of it. Most people with MB S600 W140 sedans will tell you around 10kUSD a year. To me, that's high maint. I have almost bought 3 different jag's but for one reason or another couldn't pull the trigger.
I would assume driving the DB7 regularly, say at least 5k miles a year, would result in a fairly hefty maint. bill. Perhaps the car doesn't break down on you, but if the rear struts start leaking and your gauge cluster begins to flicker, it may cost 5k+ to fix it. It's just a matter of figuring out how much per year it's going to cost to keep the car going in the condition you want in the context of what you are going to use it for.
In relation to other British cars of the time, I have also heard the 6 cylinder model especially is fairly durable, but I have no idea what that really means coming from Jag owners who's cars depreciate 50% in 4 years or less.
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:redface: 
