That is a great idea Sashwa! I have never worried about top and bottom swapping. I keep my batts marked in pairs, but pay no attention to which was top or bottom when I take them out, put them on the charger, or put the charged ones in my batt holder. I figure they get mixed around enough

I have 6 sets that keep 2 BPs going every day.
All but 1 of my sets are the grey jacket Ultrafires. The 1 set of powerizers I have does last longer, but I have a drastic drop off in about the last hour before they kick the bucket, so I change them when I notice the drop in performance.