I had the same set-up as yours for more than a year (and then I added a Beolab 11)
Tastes in our family vary, most of the family are happy with the default operation which is all speakers are active ( BV8+BL3 (+BL11))
However I use the [SPEAKER] soft key on the Beo4 to switch between these modes:
1/ for just the news and programs like that I use [SPEAKER]+[1] = just the BV8s speaker
2/ for music (either TV programs, DVDs, or music played via LinkPlayer etc) I use [SPEAKER]+[2] = just the BL3s (and now the BL11 in a daisy chain)
3/ for movies I sometimes use [SPEAKER]+[2] or
4/ if I want bass/special effects emphasis I will use [SPEAKER]+[3] (BV8, BL3, BL11) at high volumes
First B&O (1976) was a Beogram 1500 ... latest (2011) change has been to couple the BL11 with the BL6Ks *sounds superb*