Hello to all of you,
I am a new user of fairphone 6 and I was wondering if you were up to date regarding your android os.
If so, does it slow down your smartphone or not ? Fairphone offers at least 7 android updates but I am not sur that it would be interesting to update each time as the components won’t be upgraded and the newest android version could be too “heavy”.
Welcome to the community forum 
You’ll find plenty of discussion on this subject in the forum, please do read around. I offer below, a few ideas to consider.
Short question: “Should I apply updates?” | Short (standard) answer: “Yes”.
However, every time you cross the road, you look both ways, and sometimes you have to wait. When it comes to updates, you should also look both ways, for each update, just as you do each time you cross the road:
Many people prefer to wait a while so see whether new problems arise with an update.
However, if an update solves an important problem you’re experiencing, then you’re probably going to want to install it.
If you’re a careful user who checks in detail the provenance of unexpected e-mails, who checks carefully a web link before clicking on it, who finds out in detail about new software before installing it, then you can probably afford to wait a bit for reports to come in from the community before performing an update.
If you mean that the new version might slow down or reduce the performance of your phone significantly, as a rule, that’s unlikely (apart from bugs of course, which would hopefully get fixed). Look how long some people are able to keep their phones.
Bugs apart, the main reasons for performance reduction are generally the accumulation of unnecessary apps and data, in which case the solution is in the hands of the owner.
I think (!) the user wanted to draw a comparison to the Apple iPhone where it frequently occured when you have a version with small memory that updates are simply too big to fit, and this blocks all subsequent updates, too - basically EOL your device 
I do not think this will happen anytime soon on the FP(s) because they got plenty of storage.
Well, you will always have to upgrade, because the old version will not get security updates anymore.
Thanks for your answers.