Depends on how much you are willing to pay for it. 🤣😂🤣

But, on a serious note, it will have real and nontrivial costs associated with it. Technically it is not the most complex thing to implement and will highly depend on the use case and requirements:
- Minimum desired length of time
- Maximum desired length of time 
- Media types
- Strictness of expiration 
- Ability to “resurface” 

Depending on the problem you are trying to solve, it may have impact on implementation. Complexity and maintenance will add additional costs, as well as longer term consequences of lingering dead links (hits are not free for us). If you are interested in making Damus exclusive feature, then let’s talk and see where it takes us.