With Odoo 17, Customers will need to review and sign one Quotation per period.  

If your Customer insists on being able to sign a single document, you can create one with the Sign App that incorporates some or all of the PDF pages from each individual quotation (see the documentation about PDF splitting and merging).  

We also understand not everyone will be excited over the change.  It is of course possible to customize Odoo if you feel there is a strong ROI (cost / benefit ratio) for your requirement.

From the Release Notes at https://www.odoo.com/odoo-17-release-notes

The rental period of all products on a single order is now the same to simplify the flow. This does not prevent the pickup or return of products at different moments. 

From the Product Owners discussing Odoo 16 - "Currently, we allow Users to define a rental period on each line, it allows more flexibility but it leads to complexity we want to get rid off in order to ease future improvements as this design prevents us from building a simple and powerful application. Problems with the current design include: period is required on Quotation Templates, optional/accessory products; rescheduling must be done line by line; we want to leverage the ability to add multiple products at once to an order [new feature]; we want to integrate rental and stock. When looking at four competing offerings: two of them allow only a single period; one has a single period in the back end while the front end allows a different period but it must start of the same date; the other supports different periods but with a very complex subproject concept."

When evolving Odoo, our Product Owners consider (among other things)

• feedback from Customers, Partners and App Experts (Odoo Employees who are Power Users)
• competing products and trends in the market
• historic support resources required for a given feature (tickets) including what confuses or trips up users
• maintainability and technical debt (complexity of code / lines of code)
• scalability and performance
• the evolution of technology (libraries we can use to improve our product)
  

See also:

https://www.odoo.com/documentation/17.0/applications/finance/documents.html?#split-pdf-documents

https://www.odoo.com/documentation/17.0/applications/sales/rental.html

I have exactly the same issue. I wasn't aware of this change. Made the upgrade and can't use it anymore...