The show should have ended with the sixth season. You could probably pare down the number of good shows from the ones there now to maybe 16 or 17. But then it would be tricky to fill the remaining 7 or 8 slots.
It would be easier to end the series with the seventh season, drawing shows from the last six, including the seventh. Two-hour shows would appear later as TV movies. The finale should be some 2-hour movie with McGarrett finally nabbing Wo Fat, not the current one.