myhobbyshop, I can't comment on your blog (for the life of me I can't seem to figure OpenID out), so here is my the comment I'd like to make:
"Great post - it got me thinking. I have seen a trend in page views and time renewing, with afternoons/early evenings generating the most views, which aligns with your findings. Starting a new shop, I find that it is important for me to renew more often (almost daily), but once I get more sales and more traffic, I hope to do what you plan and renew when expiring. Thanks again!"