Oh, I was thinking in terms of the cost benefit of terraforming. If you magically make the planet's atmosphere 1 bar of co2, how long would that last at a usabl

Oh, I was thinking in terms of the cost benefit of terraforming. If you magically make the planet's atmosphere 1 bar of co2, how long would that last at a usable level - say at or above 0.5 bar - assuming no replacement? If that's 10k years it's less appealing, but 1m years might be worth it.