I don't know. I thought the cubes were good at 2 months and over at 3 months. But that's just my opinion. I think the Stavin cubes need 4-8 weeks. But at a lower dose, you could likely leave indefinitely. Honestly, if I were making carboy volumes, I'd use winestix which are spendy but excellent. But my 'carboy" size is 15 gallons, so the cubes are more practical. I've never used spirals. But I think the cubes are easy to measure and so it's just a matter of finding what works for you. I see this as a learning curve. I know next (this!) year to use a lower dose of cubes. But I think the cubes from Stavin are the way forward, better than spirals, staves, etc. The measure of excellence is a barrel, but that is not practical for me.