[DennisP]

It does seem unlikely that such life forms would ever become spacefaring.

[rowanG077]

That's a separate term in the equation.

[DennisP]

Yes, but we should consider these linkages when setting values. If we assume that volcanic vent life is very unlikely to become spacefaring, we should either leave it out of the "life" term, or leave it in but lower the probability of the "becomes spacefaring" term.