Currently we have two issues, which might give us the need to drop old kernels.
Here a backport breaks some extramodules like catalyst and nvidia. This means v4.4.167 was the last kernel I was able to compile all additional modules as usual. It might take a while until Nvidia might adopt to those changes if ever.
QT 5.12 LTS
This is much more an issue than the one with linux44. Here we have now the minimum kernel as linux411 due some ABI/API changes in qt5. This would automatically kick out any kernel under linux414.
Also we still have some kernels, which are end of life tagged. Removing also them will end in linux414, linux419 and the upcoming linux420 as our kernels. So we have to see on how we deal with that …