I would save discounts for a special occasion, if you do them too often I think they lose their appeal, and your followers will start to realise there’s one every few months so they’ll just wait for the next one to buy.
I haven’t done a discount on Folksy yet, but have in the past on other sites and like you, rarely had any luck. Sometimes when the site/a group were encouraging people to offer discounts so it was part of a bigger promotion, and other times when it was just me thinking it’s awfully slow and I’ll see if I can get any sales that way.
Mostly, none of them even got one sale. The only time I had a successful discount offer was when I had a big sale to celebrate 10 years in business. Even though it was a complicated offer (I reduced the price of my paintings 5% for every year old they were) and it was in a month that is usually very quiet for me, I managed to get sales because I had a really good reason behind it so I found it a lot easier to promote, and my followers seemed more willing to share it (and it also meant some things were up to 45% off).
Since that I’ve decided I’ll try and save them for something really big… 2 years to wait until I can do a 15 year sale