I've had a phalaenopsis for about 5 years in my living room and I've never changed its substrate. The pot is transparent and I can see the bark has broken down quite a bit - it's darker and more compact now. Should I repot it with fresh substrate or can it wait? I don't want to kill it.
Is the orchid flowering right now or is it dormant? Basically, that dark and compact bark you see isn't draining water well anymore, so it's time to repot it - after 5 years it's definitely due. The best time to do it is right when it finishes flowering or is resting, because repotting stresses the plant. Use orchid-specific substrate (coarse pine bark), carefully remove the old one without damaging the roots, and plant it in a transparent pot the same size or slightly larger - it's hard to kill it if you avoid leaving the roots waterlogged afterward.
I change the substrate on mine every 2-3 years and when I see that dark color and compaction, it's basically screaming for a repotting, because the bark breaks down and holds way too much moisture. Best thing is to do it right after it finishes flowering, so the plant isn't stressed; if it's resting now or has no flowers, that's the perfect time. One thing to watch out for: when you take out the phalaenopsis, check the roots carefully for rot (those would be dark brown and mushy), and if you see them green or silvery you're good. Use medium or coarse orchid bark, nothing like regular potting mix.
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