In the end, Lam Son 719 lasted for 45 days, and the airpower was the only thing that saved the ARVN from a complete defeat in Laos. The North Vietnamese nevertheless did not get off unpunished: their losses were indeed heavy to a degree where their planned invasion of South Vietnam had to be postponned for a full year.
So, the mission took heavy casualties but delayed the invasion of South Vietnam by a year...
In the end we know in hindsight that it wasn't worth it, because the US pulled out and South Vietnam fell, and millions died. Had the US not cut off aid and ran?
Who can tell.