Paulo,

Spaghnum moss generally should be changed after 6 months to a year (at
most), depending on your watering habits and the quality of the moss. New
Zealand spag is considered the best, and some of the Chilean product is very
good. (I got some Chilean from Ray at First Ray's that was as good as the
N.Z. that I'd been using.)

If you can reach into the pot and come up with fingers full of long strands
of moss, then you're probably fine. If it is slimy, or worse, soupy, change
it out immediately. That's why I like the CHC mix; it lasts far longer.
But I still use spag, and will continue to do so. Some plants just like it
better. Go figure!

Diana