It is rumored that Apple is about to push iOS 4.1.1 aka ‘an alarm-bug patch’, which will most likely patch comex’s untethered hack. Even though limera1n is bootrom-level, you should still backup your 4.1 hashes!
Because the “untethered” part of this jailbreak comes from a userland hack from @comex, you should still backup your SHSH hashes for 4.1. Do this by either letting Cydia keep them (“make my life easier”), or using Tiny Umbrella. This way you can always come back to an untethered, jailbreakable 4.1 on your devices after Apple has closed their 4.1 signing window (they’ll close the 4.1 window once they push out their next firmware version). If you fail to do this and ever need to restore to 4.1 again, you can still jailbreak but it will be a tethered JB (you’ll need to connect to your computer to finish the booting process, each and every time).
And remember: you can backup your 4.1 SHSH hashes without even being at 4.1 or being jailbroken, by using Tiny Umbrella. If you don’t know how, check out this tutorial…