Mine have been on since two weeks ago. When temps go below 45F itis time to switch.

Spacers are only a no-no if you expect to use snow-chains. Spacers reduce the clearance between the fender and the tire and the chain could get caught.

I never use chains and leave the spacers on in the winter.

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.