BEWARE !!!!!!! AS OF DECEMBER 28TH it is NOT POSSIBLE to do the O loop without reservations to campings that are on the way
I just had to walk 50 kilometers back to the entrance because i had no reservation (and believe me i tried everything i could). They WILL stop you if you are unable to present a document with a reservation, and they have the lists of all the people who reserve, so be aware...
Please note that it has changed as the season started this month. I actually met a chilian guy who did it last week and did not have to present reservations.. so please think thouroughly and dont waste time on this (even though the view on dickson campsite is nice, its not worth going there and coming back - might as well do the grey side in one day if you have the endurance)
So, that beeing said, if you're a good trekker you can do the loop in 4 days and a half, basically you can remove 25 % of walking times no problem so when it says 10 hours its more like 8 hours and maybe even a bit less (with breaks and photos). WARNING : good trekker means you can walk 8-9 hours a day with possibly up to 1000 meters climb
You can do :
1 day mirador los torres (leave bag in camping) + going to serron (leave stuff in lodge or hostel)
1 day serron to perros
1 day the pass and going down as far as you can
1 day frances valley (camping italiano)
1/2 day going back to los torres
that way you can get back your stuff at the lodge / hostel (1000clp / day)
Also, its easy to camp without reservation at the entrance of the parc ("las torres" camping stop)
I dont know about the other camping grounds on the W but those on the O loop they check, and the rangers will block you if you dont have a reservation (see above).
Any other question, please shoot away
I'm in chalten now and god it feels great not to have to register to camp somewhere
PS if you have NO reservation at all, mirador is a one day hike
much more a problem if you want to go see grey as its much further(would be a 11 12 hours for a good hiker i think, leaving from las torres camping and without taking that (freaking expensive) boat, leaving from another place that you have to reach by bus (such a mess this park...)

