Actually, it's little different. What I meant is that you don't have to stake because you don't lose your percentage ownership in the coin if you don't stake. Most POS coins have inflation that goes to stakers, and so if you don't stake, you are losing slowly but steadily your percentage ownership of the coin. So, you have to stake.
With NXT this is not the case because there is no inflation. The stakers get payed with the transaction fees only.
But you seem to be interested to stake without having your wallet open. This actually is possible in NXT as well, you can basically lease your staking power of your coins to another account, and they will stake with your coins, but they can't spend your coins, so you have no counterparty risk.
In NXT they call staking, forging. A 'forging pool' usually takes a share of the forging income. You have to renew this only once per month or so, so shortly login and then you can close your wallet again for a month.
Thanks for the info, mate! It is good to know that you can also stake NXT without leaving your wallet open with the option to lease your coins to the other account. Still, what would be the minimum amount of NXT to have in order to begin forging? I have some NXT but it doesn't start forging maybe because I don't have enough NXT to begin with the process.
Anyways, NXT has been one of my favorite alt coins and I hope that with the release of Ardor it would be even better.