In the press conference video, in response to a reporter's question, LE said that the bodies had likely been there for 3 or 4 years....not as long as 10. I presume they know this based on how long ago the unit was initially rented.
Other info coming from the press questions:
Q: do you know the gender? A: I cannot say.
Q: are they related? A: some of these questions form part of the identification, which I am very reluctant to reveal at this stage.
Q: Can you comment on the state that the bodies were found in? A: That information is very important to the investigation and I am not prepared to comment on that.
Q: How upsetting has this been for you and the staff? A: I really feel for the family of these victims. Right now there are relatives out there that aren't aware that their loved ones are deceased, especially two young ones. As for the investigation team, this is no easy situation no matter how long or how experienced....
Q: What other kinds of items were found with the victims? A: Household items, personal items. The scene investigation there, one of the objectives was to use the other items to first and foremost confirm the link between the suitcases and and rest of the property. And once that's been confirmed to use the rest of the items to assist us in the identification of the children, and that is still ongoing.
Q: Are there people in New Zealand who will know something about this? Are you looking for people to come forward with information? A: At this stage of the investigation all we can say is that there are relatives of the victims here in New Zealand.
LE clearly knows who the suspect(s) is (are), but are holding their cards close to their chest for now as they continue their investigation.