Nah. Just act like a grandpa. I'm not really old ballz until the end of this year ;)

I actually would calculate and quantified all the numbers to make the comparison...

e.g if I have a e30 M3, low-km, pristine condition. say worth 50K now.
guesstimating all the repair & maintenance cost, insurance, future values..etc

You might realize driving the car daily for 4 years could cost you $30-40K+ (car value goes down to 15-20K, + repair costs)

it is a nice car, but $40K is enough to lease a brand new 335i/S4 for 4 years.
Do you think you will get more enjoyment driving a E30 M3 for 4 years or a 2015 335i/S4 for 4 years at the same cost?
I am sure some will prefer the E30, others will prefer a new car. Point is, once you put it into a number it makes the comparison much easier

Btw, dont' quote me on those numbers, I am just making random guess. You might find out driving the E30 M3 for another 4 years would only cost you $15K (because it didn't drop much in value + fewer repairs), in which case the cost is comparable to driving a brand new yaris.

^ only problem is you've inflated the E30 losses/costs and decreased the new cars costs. By driving two cars you're spending an extra $4k/yr in insurance on the new car (if it's a brand new 335), plus you're still paying for maintenance. On your older car the value is decreasing either way, but as westopher figured out you're only losing an extra ~25% if you add a pile of km to the clock and it decreases at a slower rate because it's older.

Using your example from above you buy a fairly reliable 25 year old car worth $50k now with 50k on it, you drive it only a little for 4 years, keep the km down under 70k, and you sell it for $40k, so you've lost $10k. You also spend $15k leasing a Yaris to DD for those 4 years and an extra $6k on insurance for the Yaris ($1500/yr). Total cost to you is $31k and you spend most of your time in a Yaris.

Meanwhile your friend buys the same car for $50k with 50k on the clock, DD's it til it hits 150k 4 years later and sells it for $32k (80% of $40k), so he's lost $18k. He didn't have to insure or lease a second car so the total cost to him is $18k and he spend most of his time in his not-Yaris.

So you just spent $13k more than your friend to drive a Yaris to work instead of your fun car for 4 years. Even if the increased mileage causes you to pay for repairs above the usual things every car needs, anything that isn't horrifically unreliable shouldn't cost you more than $13k in surprise repairs over 4 years. And even if it does go a bit over, that's a small price to pay to DD something exciting.

*I left things like basic maintenance costs and the fun cars insurance out of things because those will be the same for both situations.