Bike lactate threshold and VO2max testing

So far the only metabolic testing results that I have are on the bike. The first day Tony tested me on a spin bike with a gas chromatograph. The test measured lactate threshold and VO2max. He told me the good news was my VO2max was 64. I figured it was in the upper 50s, so I was happy about that. The bad news was lactate showed up in my breath (I was wearing a mask with a breathing tube) at a heartrate of 135 bpm. He said that was my machine-measured lactate threshold.

My understanding was that I should only be able to ride significantly above my LT for 30 or 45 minutes. I told Tony that I'd ridden for three hours last summer in the Rock 'n Rollman half-iron race at an average heartrate of 152 bpm. That just didn't add up for me. We repeated the test a week later and got identical results. So we performed a third test without the gas chromatagraph where Tony visually identified my LT on my own bike (trainer-mounted). He said it looked like my LT was 145 that way.

I guess maybe I begin generating lactic acid at 135 but have a very gradual transition into anaerobic condition. Noakes calls it lactate turnpoint in his running book, indicating that it's not really a threshold, but a point where a transition begins. I think my transition is just slow.