I'm tempted to go with a 2009 but am worried that it might fail quickly because it is only one year newer than the one I have now. Is this a concern if I buy from someone like the seller you used vs. buying a used one that hasn't been upgraded?
I had the exact same concern. I'm not sure there's a perfect answer as any hardware can potentially fail. My 3,1 still runs fine, to be honest. I just felt the time to upgrade had come.
Unless there is a hidden mechanical flaw, a failure is most likely going to be due to stressing the system with heavy loads. Obviously there's no guarantees, but I wanted to know how this system was tested. Like I said, the seller was very responsive to my questions like the following:
1. In the ad it mentions the unit has been "stress tested". Can you explain what was done for the stress test?
2. Do you have the Geekbench3 rating for this unit?
I'm just trying to get an idea of the performance of this unit and a sense of how sturdy it will be for the long term as I am upgrading from a trusty and reliable 2008 3,1 unit.
His answer (bold added by me):
1) The processors are tested with the Prime95 "Small FFTs" and "In-place FFTs" for maximum power and heat generation, well beyond anything possible in normal use. The memory is tested with TechTool Pro 8 memory test. The video card is tested with FurMark, a stress test application that again pushes the video card beyond stress possible in normal use. The HDDs are tested by writing random 1s and 0s to every sector to ensure no bad sectors and then reformatting. The SSD is tested by doing multiple file copies followed by an ATA Secure Erase.
2) The GeekBench rating is around 32K, and varies slightly depending on what else is running in OS X when the test runs.
The Mac also comes with a 30-day warranty, and even after then, I'll take care of anything within reason. I don't expect you'll have any trouble with the machine. These Mac Pros are rock solid and I would expect it to easily last for 5 years. Apple doesn't make them like they used to.
Considering your planned use, I would expect a good 2009 to last you quite a while. As for myself, I am a graphic designer/illustrator specializing in print media. With my type of work, I don't expect I will be pushing this system very hard. So, barring a catastrophe, it will probably be very reliable for a long time.
Any used purchase is a gamble, but I get the impression this seller (macmotive) knows how important positive feedback is to his business, so he came across as very honest and straight.
In the end, you have to weigh all the data and make a best guess based on your needs and gut feelings. In my case, I looked at my sturdy 3,1 and all the other older computers I hear about on these forums that still run great, and I went with the 2009 for the price point (if it lasts 5 years, that's under $600/year investment) because the odds are that it will do just fine for my work.
Oops! Forgot to answer your last question:
If the upgrades are done carefully by someone who knows what they're doing, I don't think there's any increased danger of the system going down. People have been doing these upgrades for years, and the instances of failure seem quite small (judging by threads in these forums, at least).