I'd have Lexus go through it and at that mileage make sure they do a compression test. At 250K you'll likely need replace some major components soon (Steering rack, wheel bearings, pumps, harmonic balancer can start to fail between 200-300K even with full maint). You might get lucky but they always sell them for a reason and it's generally because they get a big estimate for something.
If you only plan on keeping it 4-5 years you'll likely spend a lot of time fixing things. If you were in it for the long haul, like to make it a dedicated wheeler, it might be more worth the investment. At that mileage, you might end up needing a tranny rebuild which go on these from time to time. If you don't wrench yourself, all that stuff will blow all your savings in going high mileage.
We bought my wife's 3rd gen with 215K on it. I had to replace all the suspension, fix a leaky steering rack, redo the valve covers and cam shaft seals, rebuild the wiring harness and flush every fluid to get it up to snuff. That would have cost 10K at a shop. And since the lady we bough it from had been using to 'Jimmy's Garage', I ran into a s*** ton of half assed fixes.
It REALLY depends on who did all those services. If it's all Lexus, your in good shape, if it's random "Jimmy's Garage" you better hope Jimmy was an excellent mechanic who refused to cut corners to make a profit.