Depending on how often your trips are renting a dedicated 4x4 may be the better option to protect your 535i on such trips and from other drivers. If you get reward point or some sort of payback it may be the better part of valor. Otherwise a dedicated set of snows can make all the difference man. I had a set on my e92 M3 and did well in light precip I encountered in the greater NE in 2008-2009!
'15 F80 M3 sedan (Sapphire Black Mettalic) - Mine #1
'10 E70 X5M (Sapphire Black Mettalic) - Mine #2