Regular use of leather care products, such as leather cleaners and conditioners, will keep the leather soft and replenish moisture to keep it pliable, thus preventing creases. Can't say much about the bolster shape going out, other than maybe removing your wallet from your back pocket to prevent further indentation on the seat surface.
As far as the weight issue, I don't recall reading anything on the owner's manual stating maximum load on the seats. To those with all the advice of losing weight, overweight charts, etc..., did you ever stop and think that a person may not be overweight, but simply too short for their weight? According to the chart I should be 9ft-11in for my weight! I am just too short at 6'-2".