Because of arm, shoulder, back, and rear end pain
I developed when comutting after 40 years of riding I became attracted to the idea of recumbents on reclining seats. But I did not like bicycle drivetrain chains and was on the lookout for axel drive recumbents. I found axel drives but did not find what would work for me. But later found Cruzbike.com with regular sized chains. So I lurked on the forum for some time and read every post and practised on my bicycle by putting my legs on top of the handlebars and pretend pedalling my 'recumbent' before it slowed down too much to stay upright. I took the dive and bought a Q559 in Jan '15, but my first minute riding it I wondered what I got myself into.
But since I had done my research and read how to ride FWD (this is key) and knew that not only have many riders mastered riding Cruzbikes, and many have personal, course, and world records riding these bikes. And I had read and watched learning to ride materials on the Cruzbike web site.
So I rode around our town lake and felt better after each ride. Also did the figure eight drills. Did this every day for one week. Then feeling much more comfortable on my Q than the first ride, I started commuting to work on it and about 10 months later bought my X100. Found out that I did not need a lumbar support any longer since I did not have one to put on the X when I started to ride it. Today I am still commuting and taking adventure rides on my Cruzbikes over 3 years and 15,000+ miles later.
However, instead of getting faster as many Cruzbike riders I have slowed down since I am much more comfortable riding now not having to end the pain and numbness by getting to my destination as fast as possible. And I have started to spend more time sightseeing and 'smelling the roses'. Other's may have different experiences as the vast number of racing record finishes to this day show!
So how long it took for me depended on both how much I learned about riding the FWD Cruzbike from the Cruzbike website and later my actual riding.
You say quit with the personal history!
OK, so you asked how many miles/hours?
Ha! Depends on you!
Do your research on the Cruzbike website, reading the learning to ride postings and watching the vids, then when riding your Cruzbike; that is after the initial 'what have I got myself into', you do the learning to ride lessons starting from lesson 1 on.
Then with experiencing each successive ride, you, as I did, should become more comfortable with the FWD nature of the Cruzbike.
So, as I did to learn to ride my first Cruzbike, my Q, as Nike would say:
'Just Ride It!'