I don't really think you can say that all new cars fall apart after 100K miles. Sure, there are some iffier models, and some iffier brands, but in general, there are a lot of really well built cars these days that will go to 250K miles with regular maintenance. Accords, Camry's - dead reliable and pretty frugal on gas.

Way back in the day, Volvo was somewhat above the curve in terms of reliability and durability, but the rest of the world has caught up over time. A big part of the credit goes to the EPA - IIRC cars have to pass certain emissions tests after 100K miles, and if too many cars flunk the manufacturer might have to undertake an expensive recall. So that in and of itself has forced manufacturers to build the cars a little better.

Now I like my Volvo's, both of them ('63 PV, '93 245) but really, our 2 4Runner toyotas (wife '96, my '99, both V6 5 spd manual 4WD's) seem to be a lot mroe reliable. nothing ever goes wrong. We bought my wifes at 107K, now it has 227K, and the only non-maintenance thing that has happened the entire time is a bad rear wheel bearing. And it's not an uncommon story - people routinely put 250, 350, 450K miles on them. And they do that with less fuss than a 240 Volvo does.
--
'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)