It takes about a decade. ~15 years to be really solid.

• All of the people who supported the war in Iraq have magically disappeared. Nobody was convinced the "Weapons of mass destruction"
• People are now saying that they regret voting Trump and the UK wants to rejoin the EU (both 2016).
• The COVID lockdowns are still seen as necessary, but I'm starting to notice people openly saying they wouldn't do it again.

5 more years and I'll bet you you won't be able to find a Trump or Brexit voter and the COVID lockdowns will be seen as a mistake. 5 more years and everybody will say they objected to the lockdown back in 2020.

We haven't yet reached the 5 year mark of LLMs being big news. Rational discussion is on the fringes, but you can see it coming. At the 10 year mark all the negative issue will be plain to see and all public discourse will be negative. 5 more year and everybody will claim they never used it in the first place.