Just discovered this. I cut my hand soap bars in half and just put out half sized bars. I was quite surprised that these half sized bars seem to last as long as the full sized bar used to before. I wonder how much extra hot water we were using to wash off the extra soap before. This goes along with bigger holes in tooth paste tubes I think.
last year I bought myself some really lovely hand made soap. i as looking forward to my soap running out so i could get more but the first bar is only half gone. i just make sure to keep my bar of soap very dry except for when i use some soap to wash my hands. so i wanted to add the tip of making sure to keep bar soap dry! it apperently lasts a very long time this way. my husband always leaves the bar in the shower and it starts to dissolve very fast that way.