Question about Calibrite i1Display Pro

No. Yes.

If you leave the i1 connected after calibration, it measures the ambient light and adjusts the monitor accordingly. In changing light conditions (day/night), this actually helps a lot. It occupies a USB port, but otherwise it just stands around, and it is small, after all. Doesn't bother me in the least.
But for working with photos, it is recommended anyway to always have the same lighting conditions (not too bright, no colour effect). Then you can take the i1 down again.

I have not connected the device to the computer, but to the screen. I use an Eizo CG 222. The i1 calibrates this monitor absolutely accurately, but not via the software supplied by X-rite but via the monitor's software which allows the monitor to be calibrated directly. I calibrate the monitor in this way and can then remove the i1 again.