Yes hun because because it uses the air to dry so obviously the longer you leave it out the harder it will get. So if you can take out the amount you need or spray some water on the clay you have left out you can work it for longer. 😊
I haven't made earrings with clay but I made a pendant years ago that I wear on a chain and it's still going to this day. All I used was varnish. Only thing that has been ruined is the varnish stained with my makeup but I'm just gonna sand it off and redo it. But if you want it very strong than u can use resin.
It depends on how big the item is but it starts to become solid enough in a good few hours and completely solid in a day. I use DAS air-dry clay atm and it could be pretty dry the same day after maybe 5 hours minimum but I like to leave it till the next day because mine are a little thick and you'll have to turn it over so the moisture can dry in the bottom. Not sure how coloured clay drys and if you need to turn it over too. But hopefully this helps.
