For a grand total of 535 missions depicted so far in the Five Year Mission. And those don't count adventures told through flashback in other stories. The majority of these tales take place in the final half of the five years, but for the sake of argument that rounds to about 107 adventures per year, or one eventful mission twice every week for the entire five years.
It next occurred to me to see how many missions have been depicted for the crew of the Enterprise-D during her seven and a half years in service. If any other era had been explored nearly as much, it was this one.
For a total of only 443 missions spread out over seven and a half years, for an average of only 59 adventures per year, or about one per week. I almost expected to be surprised and find there were actually more TNG adventures than Five Year Mission adventures, but it turns out that the obvious answer is that the Five Year Mission has been explored far more than even the TNG era.
What does this all mean? I'm not sure. But at least we now know.