I have 3 'kids' cars. 2 have over 220K (1998 and 1999 NBs). 2003 Jetta with about 190K.
It's like anything - if you maintain it, it will last. But be prepared to spend some $$ on parts - good parts - for TDIs. Sure, you can hack stuff and it may work "for a while" or maybe longer. It's a gamble. Or, maybe you have a shop and can tear down fuel pumps and transmissions on the cheap.
I've done a fair amount of work to the 1999 NB. Turbo, injectors, fuel pump, starter, alternator, AC compressor, condenser and expansion valve, ball joints, struts, control arms, brakes, brake booster, vacuum pump, N75, clutch, bone yard transmission. The car has a ton of new parts and runs great - BUT - it is still an old car. You end up playing whack a mole with various other things that go wrong. So...it all depends. I bought the car used.
One thing I have noticed between the 1999 NB with a rebuilt fuel pump and the other TDIs that my kids drive - the rebuilt fuel pump made a world of difference with power (the slightly bigger injectors helped). It runs like my 2000 Jetta TDI did new - lots of torque.