One thing one should perhaps keep in mind is that while the final title rather should be shorter, the initial title can and perhaps should be more detailed to better convey the idea. Or if not better, easier to come up with for the person that proposes it.
For an actual example: some weeks ago a site with the name Mathematics Educators was started. Okay, this is a lot below the limit of 45 you might think. But, the original title was
Mathematics Learning, Studying, and Education
which has a length of 44 and does/did not feel overly long to me.
Furthermore, soon there was some discussion if one might not include Computer Science with Mathematics, too. Had OP had this idea, it reasonably could have been called
Mathematics and Computer Science: Learning, Studying, and Education
For sure this is long, and perhaps too long for the final name, but for a proposal it feels still reasonable. This is already 67 characters.
So, to me something like 75 still feels reasonable while certainly long. And, had I to decide on a hard limit for everybody I would think it wise to at least double what still seems reasonable to me.
Full disclosure: I am a proterm moderator on that site, yet none of the titles originate with me (except for the hypothetical one).