BMW uses DOT4 and it absorbs moisture faster. You can PUSH it to 3 years but I wouldn't go more than that for optimal performance. Dealer uses a pressure bleeder and it gets everything out. ABS system bleed is only needed if you drain all the fluid out or open up the system. Changing a line, pump etc
There is barely anything in there anyways like maybe 20ml. I wouldn't worry about too much. I have not changed a ABS pump assembly in ages on BMW, A couple master cylinders which does require an entire automated bleed.
Porsche GT3 992 oil change a dry fill is 8.5L.. Service fill is I kid you not 4L... 4L that's it even after a long hot drain interval