[mpg_numbers_guy]

My mom is also looking at buying a Prius. She will also be driving it about 30K miles per year. I have only seen 1 Prius that has had indicated a dead battery pack before 175K miles, and that was an '04 with 120K miles (<10K miles/yr, bad for battery health).

She's considering either a Prius or a 2nd gen Insight. The Prius would be preferred due to better city fuel economy and more room, but they're also a bit pricier used than Insights.

Then again I see you already have a 2nd Gen Insight, so I'm assuming you have a reason for focusing in on a Prius. If you get a Prius, avoid the 2010 and 2011 model years; if you get an Insight avoid 2012 and 2013 model years, as they are notorious for burning oil as they age.