With the new Office 365 Message Encryption feature helps enable non-Office 365 recipients of protected emails to read and respond with ease, regardless of the device, app, service, or identity they use to receive their email. Yayy!! that is great no longer need to download software etc but now another challenge, when recipient see this message that the link will expire after 2 months –

Joe.bloggs@contoso.com has sent you a protected message.
Read the message

This link will expire on August 01, 2018
Learn about messages protected by Office 365

Any way or form to change the expiry of link  is not available yet and perhaps by voting on Office365 Uservoice using the below link will get Microsoft to address this soon.

Allow for adjusting the link expiration time for an OME v2 encrypted message. – Customer Feedback for Microsoft Office 365