A very good friend, one mainly responsible for getting me into BMW ownership, has a 1991 535, he's owned since it was about 2 years old and had 42,000 miles. That car now has over 317,000 miles and my friend is loving it! He is thinking about just getting it painted and keeping it longer! (and he could easily afford something new if he wanted it)
I'd say go for it, if it's been cared for well enough.
2006 Honda Odyssey EXL-RES
2006 Honda Accord V6 EX-L Sedan
1999 BMW 540i 6-Speed (Sold to M3UOND on 9/21/06)
1991 Honda Civic Si - Occasional Beater