Getting invited to group boards

Hi,

Can some experienced group board owners tell me what they think of this?

I was wondering, if you ask for an invite and the owner sees on your profile that you already contribute to lots of group boards in the same niche, is he more likely to refuse to let you join his boards?
If that's the case, wouldn't it be a good idea to leave the invitations in your message box without actually accepting them before you have as many group boards as you want?

Also, can a group board owner cancel an invitation he's sent you before you've accepted it?

Thanks