Okay, as for the seven season TV series, I'll just address that issue. Technically, most shows shoot for SIX seasons. You need six seasons to go into syndication, get lots of money from continuous broadcast of your show, and so forth.
I have NO idea where you pulled the seven seasons out of. It might just be that some of YOUR favorite shows lasted seven seasons, but if you look at it, you see that most don't last that long. If you are a fox show, you don't even last ONE season (damn you bastards! you dropped FIREFLY, for what?)
Ones that do last to syndication usually run out of ideas and peter off. Some would say that Stargate SG1 was only eight seasons (seven, if you consider Richard Dean Anderson just phoned in that last season). Yet it continued on to a full ten seasons, picking up the shattered cast of Farscape and forging a new story arc.
perhaps I think into this subject too much.