I always do this. I don't have a problem with the edit function, as I occasionally use it. I do however worry I'll accidentally clear the entire conversation. Why is that even an option, much less such an easily accessible one? It is somewhat redundant and unnecessary when you could just swipe-delete the conversation from the list. This removes the whole conversation from the list, whereas "clear conversation" leaves an empty window. I can't imagine when you would want to wipe it clear and leave a blank box. Anybody?
This is exactly how I use Messages. Edit -> Clear All.
It leaves their name up when I open Messages, which makes it easy to go back to them.
To go back to the user when using "Clear All":
1) Tap Messages icon.
2) Tap user's name.
To go back to the user when using the "swipe to delete" method (Messages method):
1) Tap Messages icon.
2) Tap Compose button.
3) Start typing person's name.
4) Pick from the list for their SMS number, personal iMessage account, or professional iMessage account.
To go back to the user when using the "swipe to delete" method (Phone/Contacts method):
1) Tap Contacts icon (or Phone -> Contacts)
2) Scroll through huge list of names and tap the person's name you want.
3) Scroll to bottom of contact and tap "Send Message".
4) Pick from the list for their SMS number, personal iMessage account, or professional iMessage account.
Basically, the "Edit -> Clear All" method clears out the conversation and makes it quicker/easier to return to that person again at a later time. You can get things done *twice* as fast!
Clearing out the conversation helps performance slightly if the conversation history is HUGE and/or full of lots of images sent back and forth. It's a nice feature.