I think people have cracking cases because they do two things. One, they close the lid and let it snap shut. The magnetic "latch" is very strong on the MacBook (I'm sure you've notice that already) and unless you guide it down, it will snap shut. Letting it do that all the time will eventually break down the casing. So when you close the lid, guide it down. The other thing I think people do is they pick it up by the "front" when its close. There is already a lot of pressure because of the magnetic "latch" and then people put more pressure on it by gripping it at the front. Pick it up by the "back" or the sides.
The battery will eventually go bad no matter how good you treat it. The best way to keep it alive is to use it. Don't run it down to dead if you don't have to. Laptop (and iPod, cellphone, etc) batteries like to "keep the juices flowing" as Apple puts it. So charge it as often as possible and use it as often as possible. Just use it and enjoy it. Theres no point in having a portable computer if you're not going to use it as one
The battery will lose charge whether you use it or not. So its better to just use it. You won't hasten its death. Using it properly (not running it dead regularly, recharging it often) will extend its life well beyond leaving the system setup as a "desktop replacement".
As far as the dying MagSafe adapters go.. I have yet to see one fail that isn't the result of user abuse. If you're going to wrap the cord around the adapter, follow Apple's guidelines. Meaning you want to let the cord stick out of the adapter about an inch or more and then wrap it around. This takes stress off of the cord. Every person who has had the cord go bad at that point had wrapped it too tightly and it caused stress. Most importantly of all, do NOT disconnect the MagSafe from the MacBook by pulling on the wire! Disconnect it by pulling on the head itself or by pushing down on the head. Do not pull it by the cable at all. Every single person who has had the cord fray at that point has pulled the cord to disconnect it from the MacBook.
Another tip. If you're using it as a "laptop", don't leave it plugged in. This will also create stress on the MagSafe connector. Plus its silly to be sitting on the couch watching TV with it plugged in. Why buy a computer with a battery if you're not going to use it?
