I keep mine in the car, however I do find that they are not very breathable and are susceptible to feeling a bit damp sometimes, also the weight is not good, good bit of kit for the price, but IMO only as a spare bag
The weight is an issue but at least the straps do help to compress it down to a fairly small size, which is handy as it takes up less room in the bin.
I had one of these at a meet, first time out. I was freezing, thankfully somebody was selling a sleeping bag which i bought and had a better second night. Instead of packing it away i gave the wool blanket to luckylee for some project he had in mind, used the cotton blanket to make some charcloth and cut the zip off the outer (it had broke anyway), sewed it lengthways and now use it as a lightweight bivi bag. It seems to work ok under a tarp as a windproof layer.
update on my previous post, I have also used the bag as an underblanket after watching one of the guys on youtube using this configuration, it worked, I have also bought a second one because they are so cheap they are expendable as well