Well as some of you know, I do fb group marketing as a service. So I'm posting every day usually to different groups and using different accounts.
I use about 5 different fb accs myself and each are a member of around 1000 groups each but only the biggest of the bunch and in different niches.
For example, several of my fb accs are members of fb's biggest advertising/IM/MLM/SEO related types of groups that just about allow you to post anything in advertising format.
Where as several other of my fb accs are members of music and video / gaming groups as well as a mix of others.
Sometimes I might need to get 500 group posts in a day so I try to mix up the posting with different accounts.
Plus I always change the message after so many posts and change the link etc too.
I've hit a group posting ban so many times I can't even count.
Sometimes they only usually last for a day or so.
But that's why I have different accs I can use.
Temp bans only usually happen when you post about 50 or more group posts in the same hour in my experience.
So I only post about 20-30 with one acc and mix it up across all the accounts.
I haven't had a temp group posting block in a long time now but I have aged, established accounts.
If you're using a new fb acc and joining too many groups / posting to too many at once too fast then it will be more likely to happen.
Just go slow at first but be prepared for it to happen if you get too zealous.