Maximum loan period cannot be changed. But now that I think of it, the loan period doesn't really 'do' anything anyway. It just appears in the loan manager history list, which doesn't provide any means for selecting items due or overdue or on cloud storage about to expire.
If it's a matter of using free space offered by XYZ Cloud Storage for 3 years (e.g., a trial period), then loan the movies stored there to the borrower 'XYZ exp 2016-07'. You'll be able to make a list of those at any time with a simple search.
I've never heard of such a thing, but if it's free storage for a specific file for a fixed term, it would be better to record and track the expiry date in a custom field.