cant ppl still steal your wallet by emailing it to themselves then just loading up your wallet with their bitcoin program? you wont even have to open it or attempt to read it
Only if they know where it is and have access to it--access being:
1.) Remote, through insecure SSH configuration, lax network share permissions, etc..
2.) Local, via an insecure account (bad password/lax permissions)
3.) Local, by taking the physical hard drive from the machine.
(1) can be avoided by keeping the machine you store your key on off of your local network and the internet, or by keeping your wallet on a removable disk/drive (and never allowing the file to touch other drives). (2) can be avoided by keeping your local user accounts secure, or by keeping the wallet on a removable(...). (3) can be avoided by keeping the file on a secure media in a secure place as with (1) and (2). (1), (2), and (3) can all be mitigated by encryption, but if a thief has your wallet (even if it's encrypted) then he only needs to crack the encryption (which will
take a while) and he has your coin.
To prevent a thief who has somehow procured your ("secure") bank wallet from getting your coin, you may choose to make a new secure wallet every now and then (and transfer the funds from the old wallet to the new one). With encryption, that should be enough to prevent a thief from getting anything before you can say "Peter piper picked a peck of pickled peppers". It's up to you how long between new wallets you want to go, but I don't think you need to do it too often.
The most important point to remember is that if your (encrypted or not) wallet is ever on a non-encrypted storage medium, then it's data will remain there for anyone to scrape if they have physical access to the drive (and sometimes even without), until that data is replaced (which may take a while, unless you shred it, but it still may be there depending on the filesystem you're using). So if you can keep the wallet encrypted throughout it's entire lifetime, that would be best (particularly if it's also on a fully encrypted volume), and if you can keep it from touching your hard-drive until it can be encrypted that's good too.