Formula Needed

Many blog about it.  Many post comments about it.  Many stitch & b* about it.  Even articles are printed in magazines about it.  But, as far as I can tell, no one has come up with a formula for figuring out how much yarn to pack for travel.  What follows are my random thought on the issues impacting the formula, but alas - no formula is yet derived.

1. Crochet or knit projects.  Crochet does require more yardage.  But crochet remains (for me) much easier to correct when travel related goofs appear three rows back.  So put a multiplication bit for crochet and subtract an emotional factor for less stress.
2. Size of projects.  Obviously the smaller the project, the less yarn needed.  But completion time is short and then what?  This requires the formula to adjust for time and materials.
3. Length of travel.  It is easy to over anticipate  the amount of yarn that can be consumed in forty-eight hours.  It is just as easy to under plan the amount of yarn that can be consumed in the same time period because of the next point....
4. Time available for actual work.  Some travel is quite conducive to knitting or crocheting or even spinning.  Riding along in a car comes to mind.  So does waiting for delayed air travel.  Driving and knitting - - not a good idea.  Also the activities included on a trip must be figured in to the formula.  Hiking up a mountain in thin air - not so much time to use the sticks and string.  Chatting with family - lots of time!  It is all relative.  The formula has to adjust for available time and factor in fatigue from other activities.
5. Travel destination.  Believe it or not, some destinations do not have stores for purchasing emergency yarn stash.  Shocking.  When traveling to fiber starved locales, it is imperative to pack extra yarn.  Don't question this, just do it and call it a wild card in the formula. 
6. Time zone changes.  Body rhythms can be greatly disrupted when crossing time zones and even more so if that pesky date line is involved.  Add in extra working time due to disrupted sleep.  Huge yardage is needed in the middle of the night because the body thinks it is mid afternoon. 
7. Boredom.  Plain boredom with the same old thing.  Pack enough for the power of three.  

Likely, you can think of other factors that impact the packing formula.   What we need is a yarn Einstein to figure this out and put a handy dandy calculator on Ravelry.    Any takers?  I'll be the first to volunteer as a beta tester!