I've just started my 'third career' in arborculture. My whole life has been involved with treework. My first job, besides mowing yards, was dragging brush at 12 years old. At the beginning of the month I moved 'back home' to start a job with the city of Minneapolis Forestry department.
-Working for a private sector tree care company that pays an industry standard wage and has other qualified arborists to work with daily:
~~~Middle career---For the previous ten years I've worked for a variety of tree companies/organizations. In most situations I found a few like-minded co-workers who have a passion for treework. In some the owner did too. Other times it was so much about tenths of a percent of production costs it drove me batty. Instead of changing to a better method of working they tried to do more. Result---frustration. Too often I found that my standards for safety and production weren't accepted. In fact, too often, even industry standards were too high. This lead to friction too. Having authority but no power is not a way to move ahead. There are companies that do strive to do better. They are out there but sometimes hard to find.
-Owning & operating your own business
~~~First career---did that for 25 years. Started out as a hack because that's what I was taught. Since I didn't know any better my Evil Tom mode seemed to work for me. Once I got involved in the profession by reading trade magazines and attending workshops and conferences I realized that if I was going to be accepted and move ahead I had to change. That wasn't hard to do either. While running my tree care company I started to teach classes related to treework. This started out as freebies and over time became sort of a part-time living to my tree care company. This seemed, to me, to set things up to make a step away from my day to day tree company and into some sort of management position. It did, but I didn't find a company or organization where I fit in. It took a while to accept that I needed to lower production expectations but I struggled with lowering my safety expectations.
-Working for a municipal urban forestry division
~~~Third career---Starting out with the lowest seniority now I'm in a great municipal system. All new hires have to have prior tree care experience. 2-3 years, I don't recall since my 40 years certainly covered that requirement

There are lots of special projects within Forestry besides prune/remove/plant too. In time I'm hoping to be able to share my skills and experiences in some of those projects. Even in this short time I've used some of the sales skills that I learned when I ran my treecare company. The city residents are our customers. In Minneapolis the residents really do have a sense of ownership over their boulevard trees. Residents have come out, even during single digit air temps, to ask about what we were going to do with 'their tree'. Being able to enroll them in our long term, tree-time, view of their tree they have a better understanding of why we're doing the work like we do. This is rewarding...kind of like closing a sale on the commercial side.
I wouldn't give up my first two careers. There were challenges that were hard to get over. Bumps and pitfalls too. That said, I've had amazing opportunities along the way. If I didn't like my work so much though I wonder if I would have stuck with the jobs that I had. Sometimes I would have sold my treecare company for $100 and walked away...others, pricless.
Minneapolis Forestry is going to be hiring a few more people. When I hear about that I'll be sure to put a note in 'Job Finder'.