Video only (without any audio) size of my MPEG2 and AVC broadcast recordings of EP4 is around 14GB, so 18GB, without audio, is still a good size; anyway, I’d leave it “as is”, untouched - at least, RARed in small chunks.
Even if it’s 2011, it could still be a bit better than the overly DNR’ed Blu-ray, isn’t true?