Improper Comment Edit Timeout Behavior

We have 90 seconds to edit a comment. I thought I understood what that meant, but apparently my expectation doesn't line up with reality (and I think it ought to).

I just posted a reply to a comment, and was debating whether or not to add a little bit to the end of it. At 55 seconds left, I decided I would. I clicked Edit, crafted my response, double-checked spelling/grammar, and clicked Save. Since typing out my addition took longer than 55 seconds, it rejected my edits, and I lost what I would have added. This strikes me as poor behavior. Instead, that should be a 90 second window within which I am allowed to re-open the comment for editing, with no upper limit on time for doing so.