I don't have a G6, but i do have & regularly use a G5 (over 200 miles on it now).
They are both made of the identical materials & also use the heavier packcloth near the bottom of the pack. So, my experiences may be directly applicable to ans. your ques.
I find this pack durable enough for on-trail use. I have, on occasion, had branches scrape the pack's side pockets (if I were using a G6, the branches might have scraped the pack's body, or missed entirely since the G6 is narrower). In these instances the spinnaker fabric has held up well w/o any punctures or tears.
I regularly set the pack down on the ground. I lower it & set it gently on dirt or rocks. I try not to set it down on branches, but do lean it up against, or set it down on the trunks of fallen trees. The packcloth has held up quite well and is totally intact.
My feeling is that unless I take a bad tumble down a hill, really make hard contact with the pointed end of broken branch that doesn't bend/flex any upon contact, or slip & slide on some rocks, the pack material will hold up fine for some time to come - both the spinnaker portions, as well as the packcloth.
Also, I have carried up to 19+ lbs in the pack (though 12-15 is more typical for shorter excursions). At this point, all seams & stiching appears to be in perfect condition.
I do however, carry duct tape with me for repairs if req'd. Thus far, no repairs have been req'd.
Hope this info helps.