Thanks for the feedback.
@Saverocity - currently, my wife makes monthly contributions to her roth. Basically, she invests $5500 a year. No more but I'm trying to change that. She is very frugal already but there may be a few places she could cut back. Still, considering her income I can't complain.
@KingCoin - we already max out retirement accounts. I'm just trying to find an easy investment vehicle for my wife's post-retirement savings. I'll probably be handling the account maintenance, but she needs to decide (or at least agree to) how the money will be invested.
@will - Not sure! If I'm honest, it's an irrational fear that the day she/I invest the money, the market will somehow hit a high and then it'll be downhill from there. OK, that sounds dumb when I type it out...