Here's an experiment I did today to look at the temperature dependence. Comments more than welcome.
I prepared two lactate strips in the cold (5-8 degrees C), next to the erg, and left two lactate strips in their container in the kitchen (21 degrees C).
Did a 2km warming up. I didn't feel top form, despite the resting day. I even suspect a light head cold may be coming up.
The original plan was to do a 60 minutes, but I convinced myself that my experiment would work at any lactate reading, so a 40 minute exercise would be OK.
I rowed for 40 minutes. It was not nice. My heart rate was higher than usual. It felt hard. I had to stop after 17 minutes to get my audio going again (a 30 second stop only, just switched from "lecture" to "radio").
Average pace 2:03.7, 185W.
The plan was to do a lactate reading immediately after the row.
Unfortunately, when I stopped rowing, I got unbearable cramp in my right calf, so I spent the first minute in pain before I could start preparing for a lactate reading.
20:22 After exercise. Cold strip. Cold meter.
I did an easy 1km in 2:19 pace and took another measurement.
20:29 After cooling down. Cold strip. Cold meter.
Then I went upstairs to the kitchen and did a measurement immediately with one of the strips that had waited in the kitchen.
20:30. Warm Strip. Cold Meter.
Then I washed my hands with warm water and did another measurement.
20:32 Warm hands. Warm meter. Warm strip.
After that I took a hot shower. I mean hot. Really hot. I usually end showering by gradually lowering the water temperature until I shower off cold, to stop sweating. This time I didn't. After the shower I took a final measurement, from my second container. My 26th Lactate strip this week.
20:48 Hot hands. Warm meter. Warm strip
In conclusion, I don't think it is detrimental to keep the strips at 5 degrees. I have to believe that my 26 lactate measurements of this week were real, at least to withing 0.5 mmol/L. I think the increase from 0.6 to 1.1 while I was standing in my kitchen can be explained by the muscle lactate being cleared, temporarily increasing blood lactate.
Still leaves unanswered the question what my good steady state intensity is. I am afraid 200W is too much, but let's see how I think about it a week from now.