I have owned my 911 since September of 1993. September 23, to be exact.
I have spent a lot of money on upgrades and stuff like that (heck, I put a 3.2 in it), but in more than 27 YEARS and about 100k miles, the only things that have "gone wrong" that I needed to fix:
Warmup regulator crapped out on the CIS
Auxiliary air valve crapped out
Clutch cable broke (due in large part to my own incorrect routing - long story)
Master cylinder leaked - replaced it
CIS fuel pump was replaced due to bad wiring from PO
Headlight (high beam) switch crapped out due to running H4s
Turn signal relay died
Oil tank level sender died
Rear wheel bearing wore out - replaced it
The rest is "normal maintenance". Brakes, oil changes, etc. I know my car's history from new (it was purchased at a dealership in Stuttgart originally). It's been rock-solid reliable and cheap to maintain.