In the meantime I've restarted the process one more time. The laptop still boots straight into the Yosemite installer so I don't think the hard reboots have adversely affected the machine.
edit: It occurs to me that the longest I've waited has been 12 hours (my first attempt). I've now seen reports of 15 hour installs, perhaps I didn't wait long enough? Even if the log buffer is full, that wouldn't necessarily mean that install has outright failed... hmm
In the meantime I've restarted the process one more time. The laptop still boots straight into the Yosemite installer so I don't think the hard reboots have adversely affected the machine.
edit: It occurs to me that the longest I've waited has been 12 hours (my first attempt). I've now seen reports of 15 hour installs, perhaps I didn't wait long enough? Even if the log buffer is full, that wouldn't necessarily mean that install has outright failed... hmm