Right now with Apple not signing iOS 8.4 and users needing to restore their devices they feel that their only option is to update. But this is not true. There is ways to save your jailbreak if you want to. 

One of those ways is Cydia Impactor. This was release by the developer of Cydia a month or so ago. And what this does is restores your device back to the stock firmware you are running on the device. Note this also wipes any personal data on the device. So you will need to make a backup before you run this app on your device. 

Another tool is OpenSSH and its more of a tool that has to be combined with a desktop tool called SemiRestore by the developer CoolStar. The reason you need OpenSSH is that SemiRestore requires the ability to log in as a root user via ssh. And OpenSSH allows you to do this. 

These are just a few ways to save your jailbreak. So don’t loose a good jailbreak if you don’t want to.