I don't know for sure but I think the anti-skip time is the minimal amount rockbox will keep in the buffer. If it's set for 5 minutes as soon as you have less than 5 minutes of data it tries to read more.
In that case setting it really high will reduce battery. If the anti-skip needs 75% of the buffer it will fill it to 100% wait until it falls to 75% and fill it again. That will require more drive starts/stops that if the anti-skip needs 25% of the buffer. With the anti-skip at 25% it can fill 75% of the buffer at a time reducing drive starts/stops.
That is correct.
I think the wiki description is perhaps a bit confusing when you are thinking about iriver with its large buffer. I'm not really sure iriver even needs a configurable setting.
Having the option can be good, because it depends much on how you use your player (or where you keep it during use). E.g., I have it set to 5 (or was it 15?) seconds and that works fine for me, while for some, a couple of minutes might be needed. Basically, it needs to be large enough for the drive to spin up and start reading before running out of data to play.
Hm.. I think I updated the Wiki section on the anti-skip buffer, but that was before the crash...