Let me explain "not really precious thing" better. Apparently it's too easily to misunderstand my original phrase as "we shouldn't save stats at all".
Mnesia does it's own journalling and crash recovery and durable commits and stuff like that. Or supposedly does.
My point was we don't need that level of durability. That means that instead of trying to commit supposedly durable transaction via mnesia after each stats sample we'll accumulate changes and save them once or twice per minute. Saving itself (because it's not much data) can be made durable and cheap.