Is an update of the build environment for building addons required

How often does the Build Environment need to be updated when using it for building add-ons? Should it be rebuilt when a new Core Update to IPFire is issued or can it stay as it is. If the Build Environment needs to be rebuilt how should that be done.
I couldn’t find anything related to the above in the wiki, only the instructions for building the environment in the first place. My existing build environment in the sandbox is Core 129, so built some time ago. I need to do an update to my Bacula add-on and wanted to know if I can continue with the old environment or if I need to do a full rebuild.

To check the rootfiles usual a clean build is needed.
Core129 is very old. (I think there are two gcc and glibc updates between.)

Before you create new patches you should run
git pull
to get the actual source tree
./ gettoolchain
to get the actual toolchain.
./ downloadsrc
to get the actual upstream sourcecodes
./ clean
to cleanup the build environment.

PS: our builders always build clean.

Thanks for the input Arne.
I got some error messages when I did the git pull, about changes to the file, so I cleared my sandbox out and have started again from scratch and will follow your advice in the future to build clean.