I just put another $2,200 into my 1999 RX300 and I'm happy that I did. We're in the process of buying our first home, and neither of us wants to spend tens of thousands of dollars of our down payment money to buy a replacement car. Besides, the RX has been incredibly reliable; it's hard to justify replacing a car that runs as well as this one does.
A couple grand to keep the car in optimal condition seems like a good investment to me.