Working with recycled threads

One of the things I want to focus on this year is using a lot more recycled stuff - threads, fabrics and other textiles, as well as recycling paper by dyeing and painting on stuff I already have.  Less wastage on my conscience.  I've been looking out at Op shops, charity shops and plain old second-hand shops, for threads in particular, as they don't seem so easy to come by.  I realise they lose strength in time and may be too breakable to use if really old, but some must be ok, I've had threads for years before using them myself and they've been ok.  For an exhibition piece I'm working on, I've used as much recycled textiles (and plastic bread tags) as possible and for the next part I intend to use almost entirely recycled threads and yarns as bought from op shops or given to me.  This is a pack I found at the local charity shop for $1.