I am all about indoor cover which keeps the dust away from the car.....
You just need to make sure that the car is clean and dust free before you cover it up.
I would recommend this
PS: Your car is very used to being covered when not driven :-)
Retired: 2011 E92 M3 AW w/ Silver Novillo ZCP, ZTP, ZPP, 494, 6FL, 507, 302 & 415.....ED April 29th, 2010
Retired: 2007 E92 335i -Space Gray, Black Leatherette + Alum, Nav, ZCW, ZSP, PDC, CA & Sunshade.....ED Oct 19th, 2006