The following post is just a theoretical estimation. I strongly discourage anyone to test out this theory unless they want to risk getting banned due to spamming or plagiarising.
Also, it's a back-of-a-napking calculation... The numbers are not 100% correct, but just estimations!!!
There are a handfull of signature campaigns that pay ~0.02 BTC/week, chipmixer even goes as far as 0.0375 BTC/week.
So, i guess the top paying signature campaigns would be about ~0.1 BTC/month on average (chipmixer is above 0.1, others are below).
You're asking to make 0.6171 BTC/month on the forum... This means you would have to have 7 senior or higher alt accounts with good standing and join at least 7 campaigns, each requiring you to make 40 or 50 posts a week...
So you'd have to pump out ~300 QUALITY, on-topic, well-researched posts a week.. That's >40/day... Even if you work 16 hours/day, that's still ~3 posts/hour.
So, if you had 7 high ranking, well trusted alt accounts, and you'd get them in the top-7 signature campains and you would make one high-quality, on-topic, well researched post EVERY 20 minutes EVERY day of the month, you could probably earn about 10k/month.
If you'd take an other on-forum job, like campaign manager or escrow (in case you had an account with green trust) you could probably make some extra money on the side...
Personally, I usually make just a couple handfull of posts a week... I don't see how anybody would be able to pump out one post every 20 minutes without spamming, plagiarizing, or regurgitating something somebody else already said in the same topic... But hey, theoritically i guess it's possible.