It's a good way to learn the trade as you have to fix the things others can't and the buck stops with you.
Although I used to do 50,000 miles a year, being lazy it was handy to get paid to listen to the radio, but you can grow a fat arse.
I got to go on courses with really clever people who thought I was as clever as them as i kept my mouth shut, I found strangely enough I picked up(stole) some of their knowledge.
It handy to have as long as you need to put a job to bed as that can be where you learn the most.
Going on to a site with hundreds of boiler sales in the balance and very capable installers who know their stuff and you got to come up with the goods while you have them leaning over your shoulder picking your brains with their BS detecters turned to maximum, that's wel lhard.
Most faults are installer error, explaining that to a installers is the real art of the job as a lot of them are paranoid and think its all down to the manufacture adding inherent faults to the boilers to generate more £££ blah, blah, blah... (of courses it is) nothing to do with 14 mbar working pressure or sludge in the plate heat exchanger.
You get to hear the phrase "you're boilers ****" a lot.
I always treat a job as though it's my own house and I'm a believer in "you pay you're money it should work" but there are times unfortunately when I have to tow the party line, I always do my best for the installer/customer because as a trouble shooter if you don't have credibility your in trouble, as for the truth manufactures may be hiding, the truth is overrated.