How accurate is it in term of linearity of calibration, and how much does it drift over time?

As a diver I use oxygen sensors, and those should be calibrated once every third day, and linearity can go bad from everything between 6 months to a few years.

If I went with a DIY solution i would definitively go with 3 sensors so one can at least use voting to determine which sensors to trust, and to measure relative drift.