I do experience exactly the same. I can spin at 95+ for a while, but after some time I drop back to 80ish.
I spent (wasted?) almost 2 years trying to lift my cadence. I was doing it with so much dedication that I almost never dropped below 85. But on the very few occasions I did I had a „chainless day“.
It took embarrassingly long to connect the dots and realise I must be somewhat better suited to grind. This year I happily let my candence drop to 80 during threshold intervals, and am about 30W higher on my power curve in SeasonMatch, and already touching some of my all-season PRs of last year 2 months into the season.
I reckon Lance and Froomey have really planted the seed in our collective minds that faster cadence is better, and it‘s really hard to disspell that. Coach Chad might tell us that self-selected cadence is the most efficient, but some of us try to force the self-selection to be in the 95-105 range 
So this year I embrace climbing „en puissance“, occasionally watching a climb by Jan Ullrich for inspiration. I even go so far as introducing low cadence work in my endurance rides (gasp!). I still keep the occasional 100 rpm+ intervals as well. So far the results are very good.