Sure. Tell your users but keep in mind the feature may need some tweaking.

For example:

• The first save does not happen until 30 seconds and there must be at least 50 characters in the message or nothing is saved even after 30 seconds.
• Saved stuff is retained for 20 minutes.
• Saved automatically on Submit or if you leave the page before submititng.

So .... if you post a repy message the reply text in in the save area for 20 minutes. You go on to the read another message, click Reply. You start composing a message and enter 10 characters. Click the life saver icon and the text from the prior reply would be inserted. In other words, the prior saved text is what will be available until 20 minutes passes, or until your new message is at least 50 characters and at least 30 seconds have passed since you entered at least 50 characters.

I'm thinking the min number of characters to enter before saving starts could be reduced to something failry low, say 3 to 5... because once you start a new message it isn't likely you would need the prior post.

Even the save every 30 seconds item might be tweaked. Say you are writing a long message. You make some changes but then decide the old text was better than the changed text. If 30 seconds have passed since you changed the text, then the old text is not in the saved area, rather the text with your changes. I'm thinking the 30 seconds might be better set to 60 seconds.