If you say it like that, indeed, multiple permabans would be ridiculous, however, dear forum Gods, a forum reset with clarification of rules and other changes could be an excellent point for an "amnesty”/review.
Not sure how many of the banned ones have really committed “unforgivable sins” that warrant 1000 years of forum suspension.
1 year IMO should suffice as the max ban in most cases, people can change a lot in a year (even forum rules, or main site rules and policies, at that, can change a lot in a year). Actual trolls probably also would have found other trolling grounds in the course of that year and if they do come back, and resume trolling, next 1-year ban.
For the probably very few cases in which users do really atrocious things
(like, I don’t even know, threaten other users and their families, plotting to get another user banned on the main site, purposefully try to destroy the community, ?, such things must be a rare occurrence here, but I’ve seen it all in other places, so)
by all means, have a perma-ban (100 years should suffice, though, assuming all forum users are humans and discobot 
is beyond any shadow of doubt, rule-breaking-wise; this might change at some point when we get AIs frequenting the forum 
).
Maybe a clear separate category for “Not Fiverr-Related Discussions” could help with a few issues too, then people who only want to read about and discuss Fiverr things, search for specific Fiverr-related info, etc., could just stay out of there and save their valuable time for doings, and people who want to look over the rim of the espresso cup once in a while, or just chat about dogs or whatever, could venture there (of course, that category would be subject to the forum rules, too).
Some people might argue that the Fiverr forum should only have Fiverr-related categories, and that would be fair enough, too, but all forums I frequent/ed, do have some “General Discussion” type of category or at least one such thread going, and those tend to belong to the most popular ones and to enliven the forums.
I’d also think about making only certain categories browsable without being logged in (like the FAQ, a revamped “My Fiverr Experience”/”Fiverr Stories” category with a bit more meat than “I made a sale and got a review. THE END”), and keep others (like a potential “General Not-Fiverr-related Discussion/Thread”, Ranting Pot, Improve my Gig) accessible only when logged in.
Looking forward to seeing how the “Working on it” and “On the list” items will pan out.
Wowzers, the Forum would be a better place to be, better than Studio 54. 
