Chris, I'm something of an expert on this subject. I had bilateral knee replacement the week after my 60th birthday. I had my a right knee revision (a re-replacement) nine months later and a left knee revision three months after that. Then three years after that, I had a 2nd revision of my right knee. So, today, my newest knee is 9 1/2 years old.
I was riding a 1999 Kawasaki Concours when I had all five of my knee replacements. It was about 100-120 pounds heavier than the NT. I added peg lowerers to the Connie. I rode it to physical therapy six weeks after my first knee replacements, five weeks after the first revision, and four weeks after the 2nd revision. The last revision was a two-stage process and I didn't ride until four weeks after the 2nd stage. Even though I had peg lowerers on my Connie, when I went to Europe in 2008, I rode a borrowed Concours (in Europe it's called a GTR) that didn't have the peg lowerers, but I was able to ride it for over 4,000 miles in 19 days without any discomfort
When I bought the NT, I put Motorcyclee Larry's peg lowerers on, but learned that I couldn't get enough movement on the brake pedal linkage to actually lower the right peg. It's rotated back farther and I ride with my foot resting slightly more on the heel than on the arch. My left foot is lowered an inch or slightly more and that foot has it's arch on the pedals. I can bend my knees enough to ride with the ball of both feet on the pedals, but it's not particularly comfortable.
After the last knee replacement, I can only bend my right knee about 84 degrees. The left knee bends about 108 degrees. I can ride a bicycle again since I went to a bike shop last summer that had the bright idea of drilling a hole closer to the center of the crankarm than the normal 170cm common to road bicycles. I would guess that my right crank arm's effective length is now 85-90cm.
I'm also 5'8" with a 28" inseam and I'm comfortable with the arches of my feet on the pegs for hours at a time. My guess is that you will be, too.
My biggest issue is that I have a hard time bending my right knee enough to be able to get my butt onto the saddle so that I can lift the bike with my legs after it's decided to take a nap. That wasn't a huge issue until the last 2-3 years. I was able to pick the heavier Connie up back in 2007-2010. I could pick up the NT when I first got it. But in the last year or two I've lost strength more than I've lost the ability to bend it. When I dropped the bike in early August while on the Big Sky Working on the Railroad Rally, I was on gravel and couldn't pick the bike up. I think I could have if I could have gotten a solid placement of my feet on the ground.
My revisions were the result of a post-op infection that didn't surface until about six months after my first surgery. I was at the '03 Iron Butt Rally finish in Missoula and met Eldon Cannon (EX-WINGER) there while wandering the parking lot looking at long-distance bikes. I was on my way home and my right knee started hurting for the first time in several months. I assumed it was because I had been on my feet on a concrete parking lot. A week or two after I got home, I went to see my orthopod and he guessed that it was inflammation. He gave me prednisone and recommended physical therapy. The prednisone helped for maybe 3-4 days. About a month after that, I rode to a meeting in Winter Park and managed to get from Fort Morgan to Winter Park without stopping (173 miles). When I got off the bike to walk in to register, I nearly hit the ground. My right knee was really hurting and it didn't slack off. I couldn't walk to the dining hall (so you know I was in bad shape!) I called and learned that my doc was in surgery but was told that he would work me in the next day. I managed to get back on my bike and ride about 120 miles from Winter Park through Rocky Mountain National Park to Fort Collins.
When he examined me, he drew fluid off my left knee (which also was hurting but not as bad as the right one). It was a milky yellow. He said that wasn't good, but might not mean an infection. Then he drew blood from the right knee. It was milky yellow with red streaks in it. He cultured both samples of fluid and neither one of them grew anything. He had me do a bone scan the next week and both knees were hot. So, when he did the first revision the day before Thanksgiving, for some reason, he decided to only replace the tibial part of the joint. He replaced the whole left knee three months later. Two and a half years later, another doc did the right knee again, this time as a two-stage procedure. He removed the components the first revision and replaced them with antibiotic-infused cement spacers and my leg was immobized for the next six weeks. After that the spacers were removed and a new knee prostheses was installed. I was back on my motorcycle four weeks after that. The only problem with the 3rd right knee is that my right leg is now nearly 3/4" inches shorter than my left leg and, as I said, the right knee only bends 84 degrees.
But, as much trouble as I've had I can't emphasize how much better my life has been since I finally got that first set of new knees. My first surgeon is my current orthopod and I really wish I'd gone back to him for my 3rd right knee. I'm pretty sure that if I had I'd have legs of the same length and that I'd have more bending ability than I have now.