I agree - the bikes leave the factory in rather a restricted state of tune in the name of economy. This is an important requirement in RE's home market, India. There is a very restrictive exhaust fitted, with jets to match, giving a very lean mixture. The main modifications we make are aimed at de-restricting the bike and most of us do no more than that. Further modifications designed to make the bike perform better - usually this means "go faster" - tend to include a degree of rebuilding inside the engine, fitting special parts. In my experience, most of the problems reported in forums like this are the result of owners changing too much.
I fitted a less restrictive silencer and a larger main jet to suit it and that's all. I haven't changed anything inside the engine and have had no mechanical failures in 6,500 miles. The bike has stopped once, when a wire connection came loose. I adjusted the tappets at 500 miles and have checked them regularly since, but they have never needed further adjustment. Neither has the chain. I change the engine oil and filter regularly. I adjusted the clutch once and have adjusted the brakes twice. I have found one loose nut, on an indicator bracket. It's a case of regular inspection rather than regular maintenance.
Tom