The other thing that I use is just knowing my partner's manner of climbing. Some go all-out fast, others are more pedantic and "cerebral" in their approach. If you're out of sight of each other, and the rope's not moving, and you both have some idea of how much rope is left (which you generally should, leading or seconding), you can make some reasonable assumptions:
Lots of rope left, but moving slow? pedantic climber
Not a lot of rope left? time to look for a belay
Hit a tough move, but capable? give a little slack
Off route, and getting sketched? be prepared for air time
etc.
You get the idea.
YMMV
Nowadays, once I've clipped the piece/bolt, I say "I'm in."
Note that it also has two syllables. ==> just as in "up-rope" or "tension", you get the same result: the slack is removed.