Photo star power

I've been marking photos with stars for a while now but don't really have a system. I feel like my ratings drift over time but worse I sometimes don't put ratings on photos because I don't remember how I use the stars. This, of course, means that I am building a backlog of photos that are unrated. This wouldn't be a big deal except I am thinking of making a photo book for Grandma and Grandpa at the end of the year and I don't want to wade through a year's photos to choose the ones that should go in the book. So here's a scheme:
5 stars - outstanding photo
4 stars - photo that I like a lot but something is less than perfect
3 stars - photo that is a worth looking at again (best in a series where none were great)
2 stars - photo was a nice idea but didn't turn out well
1 stars - bad photo but one that I can't bring myself to delete

After asking Google it turns out others have thoughts too:
deeje cooley on rating systems in general
austinpreneur explains his workflow including ratings (very good write up)

I guess I'll try my system for a while and see how it goes but austinpreneur's might be better.