Mostly if a poster makes some posts within a short time, it can be spam posts which are more likely low quality. However and fortunately, it is not always true.

Another poster can open multiple topic, click on Reply, open multiple reply box and compose his replies. When he finish one post, he can spend sometime to rethink about the idea, while composing other posts. Later he can come back and finalize his replies, click on post to release some posts within few seconds. I don't think with this poster, it should be considered as spam or burst posting.

Quality is most important to consider, not how long or short time between your posts.