Agree with LoneRanger... If it says 18 drops of hardener I usually use 20-22. I work quick, but the humidity here is higher than most I'd imagine. Depending on what you used for your covering, drying times will change too (only on the first coat though).
Factors that change drying time:
Amount of hardener
Temperature
Humidity
Thickness of resin layer
What it's drying onto (fleece, wood, t-shirt, etc)
Of course there are other factors, but I'd say those are the most common. On my first layer into fleece doing it very thick it may take 1 hour before another layer can be applied.. Afterwards maybe 1.5-2 .... again if you use fiberglass cloth it shortens the drying time some.
On the back of my speaker rings I put some to reinforce them, so it was maybe .5" of standing resin, took a LONG time to dry - 6 to 7 hours and I used a ton of hardener.