I should say I can make at least 15-20 posts a day depending on my mood.
That's apt. One's mood matters a great deal when it comes to interactions. Posting on this forum is interaction (that's the way I see it). Any post that isn't interactive will obviously paint a picture of spam. Those who post in isolation – posting without addressing the topic of discussion– know what I'm saying here.
what is your average number of posts?
My average will be around six per day. This is putting into consideration that there are days are get fired up and make over 10 posts in a day while on certain days I don't even make up to five posts. Also, sometimes I get distracted from the forum and end up not making a single post.
For you what is the acceptable time gap during/while posting in this forum?
That would depend on how knowledgeable and resourceful the community thinks your posts are. I've see reputable members post in less than 5 minutes time gap and no one called them out on that. I don't know if I've fallen into such short time duration but I do like to space my posts as best as I can.
Summarily, I think what matters most is what is posted as against its time space.