From my own experience the Canon L lenses are quite resistant against vibrations and shocks. Earlier this year I was hiking in northern Thailand's mountains. During a short stop I put down the backpack to take a closer look on one of the wild orchids. Unintentionally I hit the backpack, which started bumbing down the mountain. It were about 50 meters. Half way down the tripod flew out of the backpack and during some bumps the backpack flew up to one meter or more. It finally stopped in the valley of a dry brook. It took me about a half hour just to climb down the steep mountain to retrieve the tripod and backpack.
Nothing was broken and all of the equipment still works fine. Included in the backpack were: a 5DII, TS-E 24 mm II, TS-E 45mm, Tamron SP 24-70 f2.8, TS-E 90mm f2.8 & EF 70-300mm F4.0-5.6 L, a carbon fibre tripod, a dozen filters, my tablet PC etc. Only the ball head and panorama plate got some scratches and a screw was lost. Of course the backpack collected a lot of dust and dirty during its journey. The backpack is a 5-year-old Lowepro Primus AW.