In reply to Roberttaylor:
I always say to myself for any walk "it's as far as it is, no more no less and will take as long as it does, no more no less" Simplistic but true for any individual, so assuming you know the way just set off. Up to Lognan has most vertical rise, after that its maybe 1K slightly uphill and then downhill onto glacier Flat all the way to the hut which is in sight all the time, until climb up morraine to refuge.
When younger (1970,80s) we never got lifts as we had no money, but it's good fitness training Allow 4 hrs dawdling
I've taken my kids up from valley to Winter quarters in Couvercle and it took about 5 hours for an 11yo carrying all food and most importantly drink