Biodegradable teabags

I've read complaints on this forum about teabags that don't break down in the compost bin, so I had a look at the ones I use, and the packet says they are biodegradable.  I still tear them open as I sometimes found them still intact months later.  They are Traidcraft African Gold, and I buy them online.  A bit pricey but worth it , each bag makes two cups.