Is it possible to update without having to create a new rescue drive ?

When updates (patches) of Reflect are released, it is usually not necessary to update your rescue media. The release notes (Under the HELP menu) will tell you if you should consider doing so (look for information in red text).

The above is correct, although whenever you DO choose to create new Rescue Media, it will be based on the updated Reflect version. If you want to update Reflect while retaining the ability to create new Rescue Media based on the pre-update version, then before updating Reflect, open Rescue Media Builder and generate an ISO File build. That will give you a file that can be used to create Rescue Media based on the version that generated the ISO file. You can even of course generate and store multiple ISO files from multiple releases to have a Rescue Media library if you really want to. The only catch is that the ISO will only ever give you Rescue Media based on the specific options you chose when you built the ISO file, such as Base WIM, whether WiFi/BitLocker support is included, etc. But those typically aren’t options that need to be adjusted over time after you set them appropriately for your purposes.

You're most likely already aware of this but if / when you create new rescue media, you should always test it to ensure that it boots the computer and can see all the internal and external disks that are used to store the images you will create.