Soft landing is the same as a permanent move only that you're only staying ling enough to get your SIN, apply for your PR card & complete the landing formalities. Once you get that done you can get on the next flight back to wherever you came from. There's no time duration.
You can then arrange for your PR card to be sent to you via a friend/family member travelling to where you're resident. And whenever you're ready, return to Canada as a PR with the PR card.
To maintain your PR status, you need to be resident in Canada for 2 years put of 5 years starting from the day you landed.
People soft land all the time. It's even almost as common as moving permanently.