Lifetime plan means there is no fixed end date for the plan. It will continue mining until no longer profitable for 60 consecutive days (fee exceeds revenue for 60 consecutive days). On days where fee exceeds revenue, the total payout will be zero (not negative).
We estimate that our lifetime plans will last for 1.3 years or longer. This is a conservative estimate based on projected mining difficulty and Bitcoin price. It could last a lot longer in reality.
Our non profit terms for all plans are 60 days, this means that if the daily fee exceeds the daily revenue for 60 consecutive days then the mining contract will be cancelled because it will cost more to run than it will earn.