Didn't Sunny King once say that NXT's PoS algorithm was lifted from Peercoin? I'll see if I can find the quote...
EDIT: Found it:
I thought you were the one coded the PoS in NXT. As far as I know at least the first version of NXT's PoS is a direct clone of PPC's with some modifications, appeared lacking a good understanding of the security involved in PPC's PoS. Cunicula instead always wanted a 'hybrid' system involving proof-of-work in security, whereas PPC's security is 100% proof-of-stake.
That said, you are certainly welcome to try some new ideas in the following versions of NXT.
He may have begun with a plan of implementing Peercoin's POS but no Nxt release has ever included it. He thought it was flawed due to being able to accumulate coin age with lots of low stakes. I think this is what led to the dev checkpoints in Peercoin. I'll find his quote...
Not the quote I was looking for but it serves the purpose:
Block generation is determined by previous blocks. If you are doomed to generate next block in 3 hours you can prepare a block instantly, but you have to wait for 3 hours before you can reveal it (otherwise it will be ignored by the network). You can build millions blockchains in parallel to find the best one for an attack, but at some point you will need someone else to generate a block (or wait again). Nxt uses a novel PoS algorithm, not the one PPC, NVC and other altcoins do. Nxt doesn't have their flaws.