You have to examine what the purpose of the video is in the overall scheme of things. If this is important information to the overall development of a particular competency in the class, then you are defeating your purpose to either remove it or have it go bad after a few days. Students learn in different ways. Sometime a student needs to review that video more than once to fully grasp the concept. 

I don't know if these formats exist.

Basically, a temporary multimedia product may be an advantage on one hand.

On the other hand, in the time of OER, I think: when we produce learning aids we should care for a high quality - improve them - and then offer these materials as OERs.

There's a lot of work in these videos - why not make it public?

I'm not sure if students learning will do better with temporary files - either they work/learn - or not ...

A good example for videoed lectures is Walter Lewin with his gorgeous video lessons about experimental physics!

Thanks Peter! Yes, I am all for OER, and have led the production of a lot of such materials. It would be best if all good material was open and accessible for all. But we laso have the situationof not so confident teachers, those who rather would close the classroom door, or only occasionally do a synchronous lecture broadcast. And furthermore, some teachers lead their courses by lecturing, but their lectures are more like work pieces. It is those lectures I think about, when there are demands for them to end up online. And asynchronpus provision of learning materials permits student procrastination.

The video capture and processing technologies today are capable of sharing, manipulating and preserving digital content for quite long time. Best examples are Google, Microsoft, plus other large Data Centers. The multimedia technologies used for archiving of digital content are quite advanced but yet still developing.

My attitude is to simply have a hard removal date for lecture material from the LMS, and to let the students know this will happen beforehand. They only have to see one lecture vanish from their access to realise that the lecturer means business. 

You may wish to resurrect all material for revision purposes, just before the exams. 

This raises some rather pertinent points

Personally, my lectures change from one academic year to another; indeed sometimes from one semester to another, so I can see where you are heading here. Anything posted on the WWW (in this case the LMS), has the high risk of not only making it visible, but also easier to share. With the new advances of social sharing facilities available for the net generation, the video can be shared and kept at will

One needs to consider the other end of the continuum of networking, since many students tend to choose any OER they like in lieu of the one posted on the LMS. And this can apply for total online courses or blended ones.

Also important to consider, is the query about students using a LMS when lectures are delivered f-2-f or in a blended manner? Or for totally online courses? If for the latter, the answer might be more positive here.

But to actually make a video or podcast which deteriorates over time is more reminiscent of mission impossible stuff, 'the recording will destroy after you finish hearing it' kind of thing.

Possibly the LMS admin staff might be more of help here. Who knows some such software as the MI example above might already be available. One thing one can definitely state re ICT related changes, is that ti is not static.

Perhaps in this day and age of information overload, it might well be worth spending the effort required for this exercise, to spend time vetting what the students find as OER and evaluate its quality. Interesting that the academics I interviewed All spent time evaluating ER the students found and posted on the LMS 

You have to examine what the purpose of the video is in the overall scheme of things. If this is important information to the overall development of a particular competency in the class, then you are defeating your purpose to either remove it or have it go bad after a few days. Students learn in different ways. Sometime a student needs to review that video more than once to fully grasp the concept. 

I'm with Gregg on this one. If the purpose of the video is to convey information and aid in learning, why limit how or when it can be viewed? Perhaps a better approach would be to create quizzes based on the content of the video. The student would have a hard time passing a quiz without watching the video first. And in the effort to get a better grade, this may encourage some students to review the video again and again, thus reinforcing the information. Students learn during the quizzing process - it forces the brain to recall information. I'm in an online Master's program now and I've often gone back and reviewed video and other information from the previous weeks. I'd be upset if the course material just disappeared as learning is a tiered process that builds on itself.