Raise Cash does expire. Cash earned from making purchases on Exact Pay will expire two years from the transaction date, while the Cash earned from referrals expires 6 months from the referral. Other earnings will have their own expiration timeframes.
To view the expiration date of your Raise Cash via the Raise Website, navigate to "My Account" in the top right corner and click the "My Raise Cash" option. If you are viewing your Raise Cash expiration via the Raise App, Select the icon that presents your name at the bottom and navigate to the "Raise Cash" option.