At least once every Sat & Sun during football season.
Otherwise it would boil down to location, timing and luck!
I've seen a few, but then I tend to stick to my tried and true spots during the fall because they tend to produce.
seen it about a half dozen times this year, mosly in the ditch. only once this fall. yesterday almost counts. snapper blues were actually doin arials in the breakers tryin to probably escape a seal i saw earlier. kinda cool to see. and then i caught a freakin commorant and was wrestling with the little bastard for a while and i missed the rest of the show