It's a bucket list item for me though I have my doubts I will ever do one. The longest ride I've done is 42 miles and I can it without to much difficulty but it is hard to see more than doubling that without major discomfort in my knees, neck and butt
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I currently cannot ride regularly enough or long enough to start to work towards a 100 miles. I can generally only ride 1/week from 2-3hrs max and 1 commute/week 16 miles or so round trip. Between work and work at home there is no more time than this right now