[edit] Funny that you did not even try to use search to find where sentence I mention "packet should be small (20 to 32 PINs)" comes from 
No-one should need to search a page to find all the requirements of someone asking for help, they should be in the first post. If they change, or additional requirements need to be added then the first post should be amended. It prevents exactly this kind of thing.
No no no!!!!!!
Let me repeat that -
No no no!!!
When posts get substantially edited the whole thread can collapse into total confusion. The whole history is lost and it becomes impossible to know what subsequent responses were responding to because the time relationship between all the posts in a thread are lost.
Some clearly documented minor edits, such as typos, are ok. It might be acceptable to mark part of a post specifically as containing information that may be kept up to date (such as the multimeter specs table) but that still risks some posters viewing, and possibly acting upon one version of the data and others seeing a later, different version with lots of potential for confusion.
Updating a post is great for viewers who encounter the post for the first time after the last update but is terrible for those who revisit or follow a thread, potentially (if they care enough), requiring them to reread the whole thread every time they come back to it.