For longer sales cycles, the product marketing team should be creating assets and programs that rally stakeholders, enable champions and fend off competitors during Request For Proposal (RFP) bakeoffs to help drive early opportunities to close. Long sales cycles frequently involve RFPs heavily influenced by third-party artifacts like Gartner Magic Quadrants and Forrester Waves that map out critical capabilities, functional requirements and other vectors of consideration. The PMM team should create and own a "golden" response ready to go with core messaging, up-to-date product capabilities and pricing/packaging so account teams aren't scrambling to pull that info together at the last minute. Pulling a "golden" RFP response off the shelf and making a few tweaks based on the customer is a much better path to success for account teams.
Long sales cycles often mean dealing with multiple stakeholders, so if you're selling to a line of business you'll also have to get through reviews from IT, security, legal, compliance, etc. Have spec sheets, whitepapers, demos and other artifacts ready to go for those personas. PMM needs to stay close to the account teams to understand what works and what doesn't then pivot accordingly.
Internal champions at the customer/prospect are often critical in winning long sales cycles so the PMM team should figure out what those champions need to rally their peers and senior leaders to help win the deal. It might be a reference customer "brag book" that shows how other companies in their industry have been successful using your product or it might be architectural diagrams or demos to win over more technical audiences. Again, staying close to the account teams and building a relationship with the champion (if possible) will help ensure PMM creates the right content for the right audiences.