No way of backing up shsh file of 3.1.3?

[sqtcnt]

I just got a 3GS and planning on having a jailbreak.
It seems wise to back up the SHSH file before JB but I was told Apple has made this impossible.

So I am wondering if there is any way for me to get the SHSH file?
If not, what might be the terrible consequence if I JB without backing up the SHSH file?

Many thx!

 

[grapes911]

The SHSH blobs come from Apple and are tied to one specific device. Apple is no longer signing 3.1.3 and only signing 4.0. You are S.O.L.

 

[sqtcnt]

The SHSH blobs come from Apple and are tied to one specific device. Apple is no longer signing 3.1.3 and only signing 4.0. You are S.O.L.

If I JB and failed somehow, then I can only upgrade to iOS 4? Is that correct?

 

[dhlizard]

If I JB and failed somehow, then I can only upgrade to iOS 4? Is that correct?

Correct