unless the meteor is a rogue moon, the mass gained/lost is negligible compared to other particles interacting with the atmosphere or radiating (in and out), processes which are constantly happening.

for example, just the sun contributes some 200 tons every year (We also radiate out about the same mass that comes in). in 7.5 million years, that equals the asteroid that killed the dinossaurs (an event which happens way less often). So yeah, maybe the mass changes for a while, but even then, the dinossaur-killing asteroid is 0.000000000001% of earth’s mass… If we had one meteor like that everyday for a billion years, we would get some 20% extra mass.

(rough numbers I calculated just know, double check please)