I still have a phone and SIM card I bought in the Philippines about 9 months ago. Will I still be able to use it when I get there almost a year later?

the prepaid cards usually expire after 2 months if unused. but they are so cheap now 100 peso should buy a new one with free credit.

I have had the same prepaid SIM for about 4 years despite extensive absences (up to 12 months), I just reload on arrival and voila instant service. Depends on the network I guess. 9 plus 12 months might be pushing it though, if I read your post correctly.
#2 the SIM was still activate despite not being used for 12 months? Someone must be sending you credits or load that kept your SIM active.
Usually the SIM expires 6 months after if there are no credits loaded. Read the mobile companys policy on SIM usage.

Ha CDO I wish, someone sending me load? Usually the other way around!
Seriously though all carriers have a published policy on SIM validity, usually they state a period of inactivity after which the SIM will be cancelled. In practice this does not always happen, at least not in the period stated in the policy.
So yes I still have the same active prepaid SIM cards in 3 different countries, pretty much roulette whether each is still active apart from the one I'm currently using, but so far so good. Been doing that for about 5 years now.