Acrylics actually dry much more slowly than most are aware of. They take days to months to fully cure, for the acrylic to clarify, and the more medium you add, the longer the process. Me, I use lots of mediums, in terms of both variety and quantity. Lots and lots. My Liquid acrylic colours are rarely larger than 120mL containers, while my gels populate my increasingly cramped studio in 3.78mL to 16L buckets. And I'm constantly running out.
The most frustrating part of this is the TIME! Spend 10 minutes to an hour in the studio, wait 2-3 days before being able to get back in there for the next layer. By the time the next layer is ready to go on I've already forgotten what I had planned for it to be, and something new happens. My pieces are changing, layer by layer, the direction rarely constant, the intention too often a tangent of the initial intention.
Acrylics dry too slowly. Still trying to figure out if it's a good thing, or a bad thing.