If they have been dry they should be fine if they look OK. If you see signs of rot, then you would not want to use them. So that's what you want to look for... if they have started to break down then there's no point in using them if you need to repot again in a year. So you can make your decision based on what it looks like.
On another note, how do you know if the sphagnum moss, wood bark, or coconut husk has been broken down when used by the plant as a medium for a period of time?
The things I look for that are indicators of medium breaking down are staying wet for longer than when it was new, weeds growing in it (especially bark). Also bugs like fungus gnats (that like to eat rotting material) are an indicator. Sphagnum when it breaks down starts to look "stringy", in general it needs to be changed every year or two at the most. (Bark lasts a little longer) These probably will break down faster in your humid climate than in my drier one, so you may find that you have to repot more often.