The issue here is that the tweaks being done to the contest on the fly isn't suiting your needs. If you're honest with yourself, and the changes benefited you to such a degree, then you would just be smiling all the way
I know you're not directly quoting me, but I want to respond anyway.
This one week extra is probably beneficial for me, as it gives me more time to climb up to more points, even though I am currently placed lower than I was last night. But I also know, for everone who climbs up, somesone else falls down, and for that person it makes Primedice look bad. Risking to look bad is not the reason Primedice holds these giveaways, so it should be prevented.
I hope/suggest Primedice saved the placements at 31.05.2016 20:00 UTC, and when the contest ends in a week, pays users the for highest placement they had on either one of these dates. That would be a good way to fix changing the end-date this without cutting anyone short.