>The first thing to go on my bike is the deraileur though, they keep a year or so even if taken care of
>I do buy the cheapest ones I can find for around 10-15 euro
Single speed and 3s chains last 5000km easily while 12/13s won’t last much more than 1000km.
in some number of years, 3x parts will become less available and less common on cheap bikes.
We have lots of bikes and have gone through even more (bought & sold). The most reliable drivetrain on any of them just turned 20 (2004 model). It was the highest end Shimano XT-R at the time. It is easy to align, always stays in alignment, all in all takes very little attention and always shifts perfectly.
The bikes with cheaper drivetrains are a lot fuzzier and take more frequent attention and even when freshly aligned don't quite shift as nicely.
The absolute worst is the cheapest one (a department store bike my partner insisted on buying as an exercise bike). It simply can't be aligned well no matter how many hours spent. When I get it to a good-enough state, it's misaligned after a few weeks. The amount of time wasted on that thing would easily buy at least an Ultegra set to replace it.
A derailleur can cost $10, but it won’t be nearly as durable. Buying a high quality one is gonna cost in the same neighborhood as $100.
Where a geared bike with a derailleur will need you to put the bike in the smallest gear, and untangle the chain from the cassette. Replacing the wheel back in requires the chain to be properly laced around the cassette and can require dexterity.
Unfortunately derailleurs are necessary to ensure chain tension when the bicycle frame isn’t designed the allow for manual chain tensioning (vertical dropouts).
Also, run tubeless and flats will feel like a thing of the past.
The geyser of glue makes a hell of a mess too. I went back to inner tubes.
I guess it all depends on what you are used to do. I had soooo many flats last year when the spikes started eating through my one year old schwalbe wintertires. 220 spikes makes 220 holes. Had to give up on fixing the holes and change innertube until I could get new tires. Not schwalbe this time. Don't think tubeless would do any difference here though, see enough people get flats with those too and as someone else stated, the glue can get pretty messy.
Having a properly packed underseat bag is essential to any long ride.
Also I have never run tubeless at 25mm. Most folks I see running tubeless have 28mm at the smallest.
Switching is probably a bit of an unecessary faff. But if you want a drivetrain that can be ignored or neglected and never complain, an internal gear is really great.
For a commuter bike it also allows you to fully cover the chain and chainring if you want.
Looking at jensonusa, the cheapest rear derailleur is a Shimano Altus 7/8 speed for $22.
The only problem is, is that this kind of guard typically is quite susceptible to damage if the bike falls or when you hit something.
Otherwise it is in many ways superior to a belt. Belts are inherently inefficient compared to chains.