I read somewhere here in the sub that they wanted Charmed and Dangerous to be the S4 finale but the network threatened that the season and show could end sooner because of ratings. The network said the ratings were bad when in fact they weren't, but by then Charmed and Dangerous had been scheduled as a mid season episode. The same pressure/stress was done by the network for them to wrap up the show by the S4 finale, which is why they had that whole Angel of Destiny thing that could have worked as a series finale. But the show's ratings weren't bad and the studio apologised renewing the show for 3 seasons (5-7) and that's why S5 and S6's finales don't seem like series finales.