Climbing from sea level to the observatory below Picacho del Diablo in Baja Norte, Mexico was close to 10000 feet of climbing on mostly soft and loose ground. A long day to cover 50 miles all up hill. [The road is now paved two thirds of the way up to the entrance to the national park.]
Once in the park I thought that I was touring in Yosemite NP although in a drier alpine granite environment. The views to the mainland and Pacific coast were spectacular. Signs warned of the danger of being trapped by heavy winter snows!! All this just 150 miles South of the US border.
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Another long climb was up the volcanic cone of Mount Chimborazo 20,720 feet the highest mountain in Ecuador. Climbing all day in fog, rain , sleet and snow from 9000 feet until stopping at the Edward Wymper Hut at 5000 meters/16500 feet in the snow after 14 hours. Very cold and below zero even in the unheated hut where I wore every scrap of clothing and wished for more. The views were marvelous and the descent carving through pumice fields like a skier was spectacularly adrenaline producing. Dropping into warmer air with each passing minute was a pleasant reward as well.
I have found that climbing is more dependent on your attitude than your strength. I just find a gear that I can maintain all day and then I think of other things while observing the environment around me. If you are driven by time constraints or goals based on speed you may have an unpleasant experience fighting the climbs.