If there is any affect at all on battery life, I'd say it would be a good effect. I believe the only reason Nissan would consider it for emergencies only is that it just takes too long to charge up the car. In most cases it would render a persons usable range somewhere between 30 to 50 miles per day because unless you can charge at work, that would be the max charging you could get in the evening. So naturally that doesn't sound too good for their product, so they'd rather you buy an L2.
However, if your lifestyle can tolerate the slower charging speeds, by all means, use it.
2013 Blue Nissan Leaf SV
2012 Summit White Chevy Volt