In the IEP article on infinitism, §4b, an objection to infinitism called "the proof of concept objection" is described. The problem is: if potentially endless nonrepeating sequences of reasons constitute knowledge, where are these sequences?
But scientific reasoning seems to work this way, doesn't it? We come up with a model of some phenomenon, this ends up leading to further questions about the subject, we discover further mysteries that invite new models that lead to more questions... Like, we knew about electromagnetic and gravitational forces, discovered the strong and weak nuclear ones, later discerned that these involve quarks, applied all this cosmologically to infer the existence of dark matter, then found out that there's an apparent acceleration to spatial expansion involving dark energy, presumably we'll have to refine all these concepts again and again as time goes on, and given the potential infinity of possible experience and experiment, is this sequence of scientific development a "proof of concept" of infinitism?