That's pretty much the way we set up a new install as well. The ESI 50 maintains it's programming at least as long as it takes to get to the customer site, at times this is a couple hours away. I've never bench tested battery life on these, but 48 hours probably isn't too much to ask, and is probably a safe bet.

Sometimes the thoughts in my head get so bored, they go for a stroll through my mouth. This is rarely a good thing.