I just replaced a 2009 MacPro
It had many hardware upgrades over the years - upgraded CPUs, 128GB RAM, 4TB NVME storage, a modern AMD GPU, USB3/c, thunderbolt, etc
The only reason it got replaced is because it became too much of a PITA to keep modern OSX running on it (via OCLP)
Replaced with an M4 Max Mac Studio, which is a nice and faster machine but with no ability to upgrade anything and much worse hardware resale value on M-series I'll have to replace it in 2-3 years
If you were using a 2009 Mac Pro for work until a year or two ago then you seriously need to think about how much your time is worth and how much of your time you were wasting by "saving money" on not buying a new computer.
If you're self employed, the cost of equipment and depreciation make hanging on to that 2009 system even more of a poor choice.
If you were still using a 2009 system I don't see why you'd "have to replace in 2-3 years."
I'm a former 4,1 user, myself — replaced with an M2Pro mini Jan 2023 (finally retired fully 2025).
Absolutely recommend you purchase the 4-bay Terramaster external enclosure — gives you four SATA slots that are hot-swappable (unlike MacPro's). 10gbps via USB-C.