I'm going off my experience with owning and driving the 5 series ever the last 20 years, ever since I had a 1980 528i, with a brief interlude while I drove a 325is, and my experience is that here's what happens when you spend $1000 in anticipatory repairs:
Within a week after getting your car in tip top shape, you will blow a headgasket. :o)
I am not talking about routine maintenance, which I agree at some point around 75,000k, I think you could put things like the fuel pump, water pump, fuel filter in the category of routine maintenance. I'm really not an expert but I've had no problem just taking care of things as they arise with these cars. Anyway, the truth always lies somewhere in between and a healthy discourse is good on this stuff, where experiences differ so I don't mean to demean anybody else's input but only offer my own experience.
And when in doubt, clean off the oxygen sensor ...