With a fixed quality parameter (30), regardless of the input source, will the size of the result (.mp4) linearly depend on the length of the video?

Question

Video

There is a command to convert incoming videos like this:

ffmpeg -i <path_source> -y -vcodec libx264 -crf 30 -acodec aac -ar 48000 -strict experimental <path_source>.mp4

I was interested in the following question:
Can it be argued that with a fixed quality parameter (30), regardless of the input source, the size of the result (.mp4) will linearly depend on the length of the video?
For example, if the resulting video is 30 seconds long and weighs 5MB, then it can be argued that a video 2 times longer will weigh 2 times more.
If this statement is false, is it possible to adjust the conversion so that it is true?