I use the shower itself as a gauge, because I usually steam up the bathroom, to take down flying dust-particles before hanging the negatives into the shower-cabinet.
If the shower has gotten reasonably dry (around 2 hours), I tend to check the negatives to see how uniformly straight they are and if I can see any drops (especially in the sprocket holes).
It is pretty dry here, especially in winter, so mine dries quickly, I have experienced a drop or two here and there when I have started scanning them, but I just let the strip hang about 30 minutes more and things are good.
If the film below the hanging-clips is still wet, I hang them for another 30 minutes.
I did experience not yet dry emulsion in 120 once, since I was too quick to start scanning (I always scan my negatives before putting them into sleeves) and it was easy to see that they weren't dry yet, since the center of the photo's had some kind of weird blur
I suppose you learn how long it takes with your particular set-up.
A heated bathroom also plays a big role in drying time.