on point #1, agree with you 100%
-however, the compressor will run because the system lets air out and depressurizes under normal conditions. Also, I would not believe anyone if they told me the air lines on their E70 were 100% sealed.

I observe that mine runs depending on the load as well as the attitude of the car when parked. I also observe that I don't get sag when the car is parked for many days at at a time.

simply suggesting that 15" of run time every day to re-pressurize is excessive compared with my experience

on point #2, I replaced both bags with Arnott's a year ago and I'm pretty sure that when I installed the split ring and compression nut on the bags the air line was not able to slide in and out of the bag as you suggest. I didn't torque mine on very tight to get the lines to seat securely. I did cut off the last 10mm or so on each when I changed them due to the pre-existing crimp of the previous compression fitting install.

I'm not sure how much of this line is there but I suspect I could go another couple of times with trimming the ends and still be good.

YMMV.

All good feedback