A fascinating set of questions.
The role of time is more evident as a theme. Time changes everything, whether it is Buttercup's beauty growing, Wesley's and Inigo's skills growing, Fezzik growing, etc. The same is true on the other end. Inigo's skills fade as he fails to find the six-fingered man (and drinks, and drinks). Things change less obviously with time, too; the narrative frame shows that the novel "Goldman" loved as a child is not the novel that was actually written.
As for love, we turn to Shakespeare: "love is not love which alters when it alteration finds," which is to say, true love, true passion, true dedication remain unchanged even though time passes, and even after death. That's the sweet sentimental message at the heart of this lovely book.