In MEFree30's great thread going about liner life, I gave my standard answer: "25-40 days". It will be interesting to see how people reply.
Maybe we should get on the same page with the terminology. Quite frankly, I've always been confused by the terms break-in and pack-out. Daily, I use them interchangeably, but they are really quite different.
Control costs compression. That's just the way it is. Not just in skiing, but in many sports footwear needs to be compressive and sometimes, rigid. Getting the foot used to the footwear is essential and takes time, both for the engineered material the user.
“Breaking In” the boot usually takes a strong skier about 6-12 days. This is the process of using a custom insert to secure the foot's boney prominences in the correct position in the liner. As billions of air bubbles/inch² trapped in the liner pop they create volume that holds you in the boot. Depending on the durometer (density) of the liner material, this can be a humbling process.
Think of it this way. Christy and I have an expensive mattress given to us by a cougar friend. It had some miles on it- yeah so what! To extend the life of said bedding, we are always flipping and turning the mattress to prevent any permanent divots from staying in foam that is impressionable. Once repetitive pressures have compressed (popped) the air bubbles trapped in a material, that volume will never return.
On a side note, that's why a good skier should NEVER heat fit a stock liner. It pretty much renders it DOA. Also, any strong skier should run from a bootfitter who implies that cooking a liner on the stacks will take up volume or make the boot tighter. This is never true. There are a few exceptions, but not many- I rarely heat fit a stock liner. If you are serious about liner life you shouldn't either. Heat fitting a played out liner won't "unpop" those bubbles!
A solid bootfitter is trying to create these divots by using the custom insert to secure your foot in the liner in the same position each time. This ensures an accurate break in as your foot's boney prominences are secured by the liner each time in the same position. Depending on the flexibility of your foot, something is getting crushed- your foot or the foam.
An additional side note: In every bootfit, I strongly suggest every skier and boarder watch at least a half dozen movies- standing up in their ski boots before hitting the slopes. “Standing Up... WTF!?!” I find the shock in voices funny. This comes from a guy who sits 50 weeks a year and will ski 5 trams in his new boots the first day- then says his boots hurt! The movie thing is great as it distracts you from the task at hand. To have a better Jackson experience, it is best to have a realistic expectation of your endurance for athletic pain.
Spending just a few hours a week in your ski boots will have innumerable benefits on that first pow day of your vacation.
That's why it is so important to have a custom insert in your boots. It helps gives you an accurate break in as your foot is sitting in the boot the same way each time. Without a custom insert, the foot- mainly the ankles, navicular prominence (in any) and the first and fifth met joints slop around creating volume greater than what is needed. Holding the foot as tightly as possible helps keep these areas from getting too big too fast- creating that sloppy roomy feeling.
"Pack out" is when the liner has stopped compressing and fits your foot well. A nebulous, hard to define term. While ski boot liner won't ever stop compressing, hopefully the speed at which it is breaking down stabilizes.
"Packed out" is when when the liner is played out and fully compressed. Sweat, cold, pressure from skiing and finite engineering cycles of impressionable foams all take their toll on a ski boot liner. The little air bubbles in the liner's foam can only take so much before they are all played out (popped) and the liner looses it's ability to distribute shell pressure along the kinetic chain.
Read my white paper on Compression Syndromes here.
“Break In” is the time and effort required to get the liner's foam adequately compacted around the individual features of your foot. Racy and high quality liners- as well as Intuition liners- are more dense (tougher) and require a longer, more patient break in process.
“Pack out”... the very limited time between "break in" and "packed out". The Holy Grail of fitting. Seems to last only hours or days.
“Packed Out” Your liner is trashed. The engineering cycle of the liner's foam and pressure distributing characteristics are gone. The foams have lost their resiliency and are lifeless. This usually shows up as volume. The skier over compensates with muscle actions, and well, that's when things start to entropy. Your vacation/health is at risk! Don't be cheap! Any number of poor outcomes are possible.
I can squeeze a liner in the heel and instantly tell if there is any life left.
Super tight shell fits, overweight skiers and not drying out your liners all have detrimental effects on ski boot liners. As with skiing in general, regional lingo rules, but you get the idea.
That's enough for now. I'm off today and I'll be skiing fresh Jackson Hole pow!
Thanks for reading!