Generally, yes: a heavier tripod tends to be more stable because it lowers the overall center of gravity and is less likely to tip. But weight alone is not the whole story.

For long exposures, rigidity matters as much as mass. A well-designed tripod with larger leg sections will resist flex better than a flimsy one, even if both are relatively light. More material usually means more weight, which is why sturdier tripods often are heavier.

A center column is a common weak point. Tripods without one are often more stable because the legs extend higher and spread wider, improving stiffness and reducing wobble.

Material also matters: very cheap plastic tripods are usually poor for stability. Metal tripods are typically sturdier, though very heavy studio tripods are impractical for carrying outdoors.

So the best summary is: heavier is usually more stable, but stability for long exposures depends more broadly on rigidity, leg design, wider stance, and avoiding weak features like extended center columns. The right tripod weight depends on how much gear you carry and how far you need to walk with it.