Some people say they faced problems trying to recover the coins from a really old electrum wallet... why is that? what do I have to do for not having this problem in 10 years from now?
I doubt that you read it properly, it's mostly Bitcoin Core, not Electrum where people get issues when they try to recover BTC from very old wallet files, and its mostly due to the incompatability of their files or they messed up with their back up or missing part of it, or wrong seeds or even bought wallet.dat file from someone with the hope of getting BTC from it.
The electrum wallet file is not actually wallet.dat file which can that we seen from qt is also another cause of the confusion with most of'em.
[Tutorial] How to make a cold storage Bitcoin wallet with TailsOS and USB Flash