I solo every gig and depending on how big the group and the gig's leader determines how much.

Playing jazz, I never know when I'm going to solo or for how long except that it's usually going to be the last solo in the song before the head. There may be some variation as to the where, but not much. Depending on the song, it could be 4', 8's or a chorus or two. Whatever it is, it's always improvised and based on what's happening beforehand. Rhythymic, rudimental, melodic, whatever. I pick a theme or destination and explore it. I try to remember to incorporate nuance and dymanics as well a bit of showmanship and joy in what I'm doing.

In any other types of music that I've played (pop, rock & r&b, etc), most of the solo sections were rehearsed and stayed the same with a few embelishments other than say a groove section where other percussion players are joining the fray.

How about a default, "plan A" intro that's reheased and known (and played for most shows). But if you feel a creative spark or just want to stretch out on a special night, make your bandmates aware of the potential for the "plan B" intro and go for the improvised or extended solo....Best wishes on a great tour.