Thank you guys for your responses. Just an update, here's what happened when I had it checked by my dealer.
My dealer told me right away that MMPC would replace the headlamps but with a warning that the same might happen again even with the new headlamps installed. (sort of telling me without saying it directly, "disregard nyo na lang, mauulit lang kapag pinalitan natin, sayang..." that is only my impression though.") Sabi ng SA ko, according daw sa MMPC, such occurrence is due to the climate we have in the Phils. (so they blame the weather in the Phils. for their quality issue.) In response, I told them that all owners and potential buyers of the MS should be informed about this. In my case, I was never told of this issue before I bought the unit. Moreover, I never experienced the same thing with my previous cars although they were of different brands specially while they were new.
Hence, sabi ko na lang if after replacing the headlamps, I would only expect the same problem to recur, then it is really futile to have them replaced. So it's ok with me not to replace them anymore. Instead, I asked them if indeed what they are telling me is true, I want MMPC to issue a public bulletin informing their customers about this quality issue on their headlamps and that it is due to the climate we have. Or, just a letter addressed to me personally, duly signed by MMPC na ganun nga ang mga headlamps ng Montero natin.
Ayun, agad agad, ang sabi sa akin ng SA, "Sir palitan na natin."
Sabi ko, "paano kung magkamoist ulit yung pinalit ninyo?"
SA said, "papalitan ulit namin sir kung magkaganun".
Sabi ko: "OK Good! Sige schedule mo na bukas install."
Thank you guys!