How long can thc stay in your salvia? if its getting tested by a good lab?

Many Factors: It depends on many factors: the strength/potency of the thc source, single use, vs. Chronic use, amount of body fat, how well your body is functioning, etc. Single exposures have ranged from a few hours to 1-2 days. This may be explained by how much thc they were exposed to. Chronic users have had detectable thc levels for months after stopping, probably due to body habitus and overall health.

???: Thc does not stay "in your salvia." did you maybe write this question while under the influence of thc or salvia divinatorum? Or maybe you meant "saliva" (spit) rather than salvia? Thc remains in saliva from 1-10 days after use. They usually check urine, though -- can last longer there.