About 15 three-hour sessions or so. However, I will usually rip through the toe cap on the first or second session, no matter what shoes I wear.
I do flip my board a lot, but it's not like I have full on flatground sessions. I use Jessup as well, but still have to shoe-goo after every session, and usually end up patching it up a few times with suede. I also have to replace laces every single session.
Not sure why I tend to punish my shoes this hard, but I'm on the cupsole train, so I feel like I should try to make them last. Sometimes they're so fucked up after a few sessions that they hurt my feet though, but I patch them up the best I can manage, then use them from time to time for shorter sessions just so I feel I get a bit more value out of them.