[Clipper]

Are the same people playing each day? You could easily store the cards for each player and the discard piles between your sessions so that you play one game over as many days as it needs to complete.

Otherwise, I'd either tweak the starting Level or ending Level as you are doing. It won't definitely end the game in any given time frame, though, it will just give you a better chance of reaching a conclusion. Another thing you can do is implement the option rule from the back of the rulebook that allows any helper in the final battle to win as well regardless of Level. This will remove a lot of the issues with everybody beating down the guy who's about to win, likely shortening your games.