let me add my $.02 USD...
I have had to care for a 15000lb capacity hubtex side loader that was inside a cooler room that got built around the loader after the loader was in the building, and if that side loader ever comes out of that room, either the walls will be torn down or the side loader will be cut up for scrap first. there are also a few 3000 lb capacity forklift inside big cruise ships, that have to be repaired or serviced while the ship is in port changing passengers, and do not just drive out of the ship. There is no job that CAN -not- be done at the location, the question is what is the most cost effective way to do the repair/service. I usually try to insist on a 4 hour rule; where any single job that is going to take more than 4 hours should be done at the shop by the shop techs.
Now as far as how -I- got into this trade/ career...
I have tried to continuously learn this trade, and still try to learn new things about forklifts when ever I can*, and after almost 40 years looking really closely at forklifts, the one thing I think I can say I know for sure about forklifts is that no one knows it all.
I first got into thinking that forklifts were neat machines at my father's place of business (in the 1960s and early 1970) where he had a few Yale and Barrett battery powered pallet movers that lifted about 3 or 4 feet (low lift walkie-stradle stacker) and then signed up for the US Air Force before I could be drafted. I had a 'guaranteed' job that sounded great in the job description (corrosion control tech), but when I got to through basic training, and they explained this was the guy who washes the air-planes, I asked if there was any thing else I might be able to qualify for. and as I had been to a 2 year/3 hours a day tech school to learn auto and boat mechanics, they gave me a test and then a tool box and pointed me in the direction of the forklifts. One of the things I have observed since then is that, no matter how much I try to get away from looking at forklifts, it seems that this industry drags me back into it (I usually claim "dragged me back kicking and screaming all the way), and seems to me to be one of the most 'recession proof' types of jobs.
No matter how you count it, it is cheaper to move your goods with a forklift than to move them by hand, and that is one of the main reasons why even when the rest of the economy is in the bottom of the barrel, there is still work fixing forklifts, even though the customer will be slower to pay, and search real hard for a less expensive alternative, in the long run, if you are doing the work in the manner that is most cost effective for the customer, even their search for a less expensive alternative will work in your favor to bring even more work your company's way. (But I digress)
*= one of the best things about forkliftaction is that there is discussions where I can learn from other techs, and it is one of the main reasons I prefer to discuss forklift problems in a forum like this (rather than directly mailing each other) is that we can learn from each other, and correct any misconceptions of wrong opinions we have.