A Question about Android Market Apps?

[Anoneemooz]

I have a Samsung Galaxy S on Eclair... I've recently purchased several apps. My question is, when I flash my phone to new firmware (or update it via Samsung Kies) how do I reinstall all those paid apps? Are they connected to my Google Checkout account so I can just simply redownload them without having to pay for them again? Do I have to back them up myself somehow?

I really need to know this before I decide to update once the official Froyo update comes along.

Thanks in advance!