As the resident numbers geek, I'm sure no one will be surprised that I have a complete record of vertical skied since I started in 1976: http://bestsnow.net/vertfeet.htm . As a beginner/intermediate it seemed a good measure of my progress and stamina when skiing. By 1978-79 I was on advanced terrain more of the time and from that time onward I would tend to favor the ungroomed terrain. Average is just under 20K per day and has not changed much over the past 30 years.
After all, none of us call it quits after one really good run... we get back on the chairlift for more runs. Tracking vertical is a numerical representation of the phenomenon of getting back on the lift and making another run, because there is more marginal utility in pleasure to be experienced from ADDITIONAL runs, which translates into additional VERTICAL, something that can be quantified and measured.
This is the point I make to many people when they ask about these records.My preference for terrain and snow drives where I decide to ski. If terrain is interesting, conditions are good and I'm having a good day, I'll tend to ski more. On an exceptional day I'll ski as much and as long as i can. So in my case there's a very strong correlation between quantity and quality of ski days. For an individual comparing one's own ski days, vertical is a useful measure. Comparing my vertical to someone else's is not so useful since their preferences/priorities in skiing may be different.
The situations where vertical is not so good as a measure have been mentioned already. If you're lapping groomers on high speed lifts the number easily can be pushed higher (I call this "cheap" vertical). The 3 days this past December notwithstanding, it's very rare that my days are primarily groomers. My record 45,900 at Sun Valley was on a trip when off-piste conditions were crappy. If asked what my best endurance on skis was before this year, I would answer the 41,250 at Snowbird during the 2002 Olympics. Snowbird off-piste verts are rarely cheap.
The other situation is backcountry, completely an apples-and-oranges situation vs. lift served. I had only 7 lifetime days in the backcountry before 2010-11, but needed to do more in preparation for Antarctica. I would now answer the endurance question with my June 2011 tour on Mt. Shasta: skinning with full pack from trailhead at 7,000 feet to camp at 9,200, then climbing on skins and crampons the next day to 13,200 and skiing down. 6,200 of backcountry vertical is way tougher than 40,000 of lift served. Whether it's more fun is a subjective opinion.
Maybe an additional boost for powder, say +1 for each foot.
Readers will note on my vertical foot page referenced above that I estimate this too. I'm stricter than most people with this estimate, as I'll try to not include vertical lost in traversing to or from a powder stash. Vertical + powder vertical is the best overall simple measure of ski quality IMHO. If I rank the very best days lifetime by this measure, it certainly matches my subjective opinion. Top 2 are 28+26 with Chugach Powder Guides on 3/25/2007 and 35+18 at Mammoth on 4/9/1999. Both of these were blue sky, waist deep powder days after it dumped the previous 4 days.
With regard to cat and heliskiing, my 22 heli days have averaged 18K and my 44 snowcat days have averaged 12K.
Edited by Tony Crocker - 1/1/12 at 9:36pm