Lol, at my early hiring days (which is kinda funny since I really just started 1.5 years ago), I had one experience where I did look at 'available now' coz the guy I had planned to have a session with just decided not to see me (it's all good, we're friends now), so then I was checking my plans B, C, and D in that order to see if one was available - couldn't waste a properly cleaned hole for the night...haha.
I guess now I am lucky enough to have some of them reach out a few weeks in advance to let me know when they're going to be in town so I can get those sessions scheduled in advance. And good thing for the existence of thrusting and vibrating dildos and the Pulse for the instances where I turn into those "I'm horny now" thirsty dudes. And yea, not into 'available now' either nowadays coz God knows how long it takes to friggin' prepare down there.