I don't know, I feel like not spacing it would make things a lot more confusing and such. Your idea would make it so that threads constantly get posted in, and in the long run, "popular" members would have their threads alive whilst the others die off. With the 10 per week idea, we can prevent that. Perhaps we can increase the number to 20, but I wouldn't go further than that.
Edit: wait, no, something wasn't cleared up. With the original 10 threads per week, would the old threads get locked at the end of the week while the news ones are made?