Is it considered OK to cut a roll (120 in my case) into a bunch of shorter strips, stack them up and put the whole lot into a single slot on an archival sleeve sheet? That way I get four rolls per page, which saves me bucketloads of room (and makes the sleeves 4x cheaper!).

It's not for chromes of course 'cos I want to see those. But are there any archival problems doing this for B&W or C41 negs?

I note that if you took 35mm film to a consumer lab any time in the last 30 years, you got all your negs back in a single paper sleeve that's on the back of the 6x4 print folder. So it's probably not that bad, or is it?