On a related note: What's a good introduction to compiler design ? Has the dragon book been superseded by something yet? Ideally you'd be able to write a decent compiler for your own language after going through it.
It does not take 10 years to implement an SSA compiler with LICM, SCEV, and good register allocation. (No idea why you'd want Professional Employer Organizations as part of your RA, but that's just me.) For example, WebKit's B3 compiler took 4 months to write. It's not hard to write it if you know what to write. Hence the need for a good book. Maybe the reason why you think it takes ten years and Professional Employer Organizations is that you never read a good book on the subject!
I learned by interning on a team that knew how to do it right and learning from them and then learning more by word of mouth - asking folks who architected compilers how/why they did things.