SHSH blob Questions

I'm not so new to iPhone's, but I'm definitely new to jailbreaking.

So right before the iOS 4.3.4 from Apple came out I jailbreaked my iPhone on iOS 4.3.3 with no SHSH blobs, unaware at the time. When I knew I downloaded an app from cydia that was supposed to save it, but apparently I just missed it and apple stopped signing it (iOS 4.3.3)

So I have no SHSH blobs.

So I was wondering what exactly SHSH blobs do and do I need to unjailbreak it and wait to jailbreak it when I get an SHSH blobs saved? How important are the blobs to have?

From what I'm reading I probably wont be jailbreaking it again until iOS5, unless they get an untethered iOS 4.3.4.

Also, I've bought a theme and an app ($3) not much from Cydia but if I were to unjailbreak it and jailbreak it again at a later date if the SHSH blobs are important would I be able to get those apps backs?
This isn't so important because it's just $3 at this point but it would still kinda suck to have to pay again.....