I have the Scratch & Newton Hutch Hugger and Hutch Snuggle, and I keep the snuggle on all year cos it's supposed to keep them warm in winter and cool in the summer, and it has a detachable flyscreen.
I took the Hutch Hugger off a few weeks ago, which is basically a waterproof cover with a plastic cover over the front, so up until then I was covering them at night, but now I'm not.
If it gets cold again - which it undoubtedly will - I'll put it back on! It depends on the weather as to when I'll put it back on permanently, but it'll probably be late October/November time.
xxx