Stormfeather Variance Question

[snyder43]

Stormfeather has a 18 +-1 h spawn timer with the chance to skip (up to three times). Does this mean that if SF skips, the "new" spawn timer would be 36 +-1 h? Or would it be 36 +-2 h since the SF that skipped could have "spawned" anywhere in the first window? If this is the case, then if SF skips twice it would be 54 +-3 h and if he skips three times the spawn timer would be 72 +-4h.