It's true as long as the blockchain of the fork is still running. For instance, Bitcoin Gold (BTG) I think suffered from 51% attacks. This is what happens with altcoins, eventually it becomes profitable to attack them. I reckon the attacker stole a bunch of coins and mixed them with Monero, he was never caught.
Yet Bitcoin Gold still keeps on ticking
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
But very true, while you don't need to hurry with getting your fork coins, there's also a chance that they won't be worth much once you get around to extracting them (case in point: the current bear market).
Also be sure to NOT install any of the software involving altcoins within your computer, use a separate computer. Also DO NOT enter your private keys on websites which claim to give you access to the fork coins to claim them.
I remember Bitcoin Diamond for instance, was compromised and a total disaster. [...]
Something similar happened with Bitcoin Gold:
https://bitcoingold.org/critical-warning-nov-26/OP, the above comment by cellard should be your main takeaway. Assume that any fork coin wallet is compromised and take care of security accordingly. Lest you get your coins stolen:
https://bitcointalk.org/index.php?topic=5080741.0