I'm on my second LS400. The first was a 1990 model which cost me money on brakes and bearings (and tyres ).
Unfortunately after a disagreement with a BT switchbox and a lamp-post, the poor girl was written off. (She was still fully drivable though!)
I then got a 1993 model as a replacement and have done around 25,000 miles in her. To date, the costs have been rear coil springs and brakes.
For both vehicles I've managed to avoid the costly cam belt service so far, but am expecting a "big" bill in around two years time.
The cars are extremely quiet and comfortable, but not such a 'drive' as a our BMW 730.