2008 Toyota Corolla New Cars Shouldn't Make Noise

Last year in March I purchased my new car from a Toyota dealership. A 2008 model assembled in late January 2008. After driving it for about 1 month it started to make a weird spinning, squeek/rattle kind of noise on start up. I took it back and they said "yeah, yeah the belts were loose" so they tightened everything up and sent me on my way. Maybe 2-3 weeks later the same noise returned. I took it back, they had another look, couldn't find anything wrong, so they said "oh we adjusted the belts again it should be ok now". Again about 2 weeks later I took it back for a 3rd and final time huffing and puffing asking "WTF!" They kept it overnight, spoke to the "Toyota experts" and came back to me with "We have spoken with Toyota and they believe the noise is caused by a drop in oil pressure when the car stops, the noise is harmless and will not affect the running of the car, if the noise changes or lengthens, then bring it back. It might just need a little breaking in."
With that said, now. Over a year later the noise has not changed and I have had no trouble with the cars performance. My only concern is that I don't believe a car makes noises if there's nothing wrong. And everyone I have mentioned their final answer to says that that can't be right. Can this drop in oil pressure put strain on some other part of the engine and cause failure, say. After my warranty runs out?
I bought this car with the knowledge that Toyota (Corolla in particular) cars are one of the the most reliable cars on Australian roads. But I had to get the only brand new one that sounds like a piece of junk when I start it (8/10 starts). I can deal with it if I am reassured that this is perfectly normal. But the answer they gave me just left me feeling like they just couldn't be bothered fixing it properly and only wanted me out of their hair. I do have a recording of the noise if this will help you understand what I'm talking about.
Thank You for talking the time to read this.