I try very hard to make sure items arrive safely and quickly. The postage I charge is the amount figured by listing calculator. I always combine items to save on shipping since I hate paying to much too :)
Even a broken clock is right twice a day.
If you wear a watch you'll always know what time it is.
If you wear two watches you'll never be sure which watch has the right time.
Personally I don't wear a watch, time is relevant to your current situation and can't ever be controlled.