Lucic would be fine at 5-6 years about 5 million a year.
The problem is, he most likely will not sign a contract like that. Lucic will ask for top dollar, and a long term contract. Nothing wrong with that, except the Kings can't afford to give it.
If the Kings are willing to go 6, why not go 8 years if the AAV is around 5? Even Doughty will be 32 after 6 years, and its unlikely a 36 year old Carter and 34 year old Kopitar will be dominating down the middle. Quick will be 35, Muzzin 32, Martinez 34, etc.
That's also when the CBA comes up for renewal. Throw in an expansion draft or two in there to potentially lose a bloated contract, and 8 years is a no brainer if it keeps the AAV low. I doubt it ends up at 5, but the Kings could stay under 6 and still compete with other bidders. A 6M max contract is the same as 7 years at 6.86M.