These types of threads are becoming known for spam. It was mentioned below in the Forum Spammingthread about sandbox spamming.
It is becoming a problem that people keep posting to a thread when there is no one else posting before them. This is also considered spamming, and it needs to stop. This will be the first and only warning about the matter.
As for members who keep posting to a thread when there is no one else posting before them. I usually delete all but one of the posts (in the event you're wondering where all your posts went). Though posting guidelines are somewhat slack in the Sandbox, there are still rules for posting in the Main Forum.
As a general guideline please see this page: Forum posting guidelines.