No doubt you've lost you lost your acclimation to altitude gained during ski season. My experience as a Denver area native and having enjoyed the high country for 40+ years and owning a place at 9700 ft for 20 years is it takes at least a couple of times per month at altitude for me to remain acclimated.
For me, that generally means playing and sleeping at altitude 4-6 days per month. Sleeping up high is better than day trips as the additional time allows your blood to adapt to carry more oxygen.
If I don't go up for a month or two during mud season my I will lose my tolerance to altitude and it will take a trip or two to get it back.
If not feeling well at altitude usually folks will quickly feel better when they return to their home elevation. It seems unlikely it was the altitude alone that made you feel like crap once you got home. The additional effort required at altitude leading to increased exhaustion seems more likely than the effect of altitude after returning to Denver.
Hiking up high every weekend will certainly help. There's a benefit from every bit of time spent at altitude. Think about making a day of it (as you do skiing) to spend more time at altitude during each trip. Also, consider staying in Summit County or Leadville for prolonged exposure to high elevation to prepare for ski season.
Tylenol or Ibuprofen works well for altitude-related headache, but ibuprofen was better proven at preventing AMS last I checked:
We'll routinely take ibuprofen and give it to our kids to help with sleeping at 9700 ft, particularly the first night.
Altitude certainly becomes more difficult as we age. I'm still good but my wife struggles more, particularly with the dryness. My parents in their 80's can't go up anymore, and a number of family members won't go up after years of summer family reunions up high. It's no fun to feel like crap.
I think it's a matter of fitness, maintaining acclimation, and a bit of good luck that will allow us to enjoy the high country into old age. I'll routinely see what I assume are Summit County locals in their 60's and 70's that I can't keep up with riding Vail Pass. I hope to be one of those guys when I grow up!