I do notice an increase in problems with the glass I mail out around Christmas. The breakage goes up to maybe 0.5%, from 0.1% the rest of the year so really not much of a concern. The most difficult to ship product is the didgeridoos, which are a 5 ft long glass tube. I double box them and can ship them all the way across the country without problems but it's the only product I disable international shipping on because that seems like it would be asking for trouble. On all my other products I've actually been reducing my shipping box sizes and the amount of padding because the breakage rate is so low. I was much more paranoid about it when I first started doing online sales.
I haven't ever shipped palettes but I frequently receive them and that's actually where I see the worst breakage. I think the culprit is the forklifts.
The bigger problem for me is the packages that either get misdelivered or stolen. That goes way up around Christmas. It ends up being time consuming to deal with the customer and the postal service trying to figure out if it can be recovered before I have to resort to giving a refund. USPS refuses to take any responsibility even when their geotracking shows the package was delivered to the wrong address.