I like having viewable archives, but it's certainly not necessary. And if you can extend the sb tab to show messages from a week ago, I think that's a good alternative. It's not the end of the world if the archives are removed, and I think the reasoning for their removal is more sound than the...
There was a time a few months ago when I wanted to find certain SB messages from like March or April 2015. It was nice because I was able to go into the SB archives and track them down.
That being said, most people aren't going to want to dig through over a year's worth of messages to find a...