Let's say I plan not to use my rMBP for a few days (5-7), is there anything special I should do in order to keep the battery in good condition?
No. 5-7 days is way less than an extended period of time @FoamyBeer refers to. Imagine that a lot of devices stay in warehouses longer than the time you want not to use your MBP. Just handle it as if it was a book:
- Don't drop it
- Neither heat nor freeze it
- Keep it dry
In addition to that, do NOT leave it with a discharged battery. Actually, it's no big deal to have it connected to the charger the whole time. If your going on vacation, disconnect it from the charger to prevent damages by lightning strikes.
Apple's advice if you're storing a device for extended period of time, is:
- do not fully charge or fully discharge your battery, but charge it around 50%
- Power down the device
- Place in a cool moisture-free environment that's less than 32° C (90° F)