A few months ago I sold an item that weighed just under 4kgs, so by far the cheapest option was to send it by standard parcels at a cost of £8.24 which takes 3-5 working days to deliver (actual cost by royalmail!!, also incase some buyers dont know paypal still charge you a percentage of your postage fee, so in reality it cost me more than I received to post it, but as it a relatively high charge I didnt want the buyer thinking I was ripping them off).
When it was received although I received positive feedback,I could tell my dispatch time rating had dropped down from 5 to 4.5 so I knew the person had probably given me a four, which considering I had emailed them to say thankyou for the payment and that the parcel was on its way (the very next day I might add) I found a bit odd.
Out of curiosity I emailed the buyer asking why I had been penalised, she told me that she had purchased some items after mine and received them first which is why they received a 5 and I got a 4.
That comparison would be fine if my item was sent First Class as the others were, so obviously wouldn't take 3-5 working days to turn up, but more like 1-3, or she was happy to pay £12.50 which would be the actual cost to send a 4kg item first class.
It's really frustrating when buyers use received time to judge dispatched time, when they are two completely different things, especially when two completely different delivery services are used, which ultimately saves the buyer money, and as a result they penalise you for it.
I hope this helps some other sellers not be penalised, and I also hope this gives some buyers a better understanding, and might make them think before they act next time.