If it works, don't break it!
The square wheel never did take off, though its inventor insisted it would stop far more quickly than the original round version, and he was probably right. 0 to 60 might have been a problem though!
You often hear of actors who leave a successful series because "they don't want to get typecast". Never mind the regular pay cheque!
So how important is it for a writer to create a series once he, or she has found a successful formula? That's always supposing you find the formula in the first place!
Most successful authors keep the round wheel rolling: Examples.....
1. Terry Pratchett's Discworld books are unique in that within the series there are around four formulae, all of which have well-loved characters. I asked him once how difficult it was to create new DW plots after so many books and he said it was becoming easier as the characters tend to write their own plots and books now, He just puts them in situations and off they go!
2. Bernard Cornwell's Sharpe books are some of the most formulaic (and best written) stories. Sharpe is sent on a mission, he makes an enemy, he meets a woman who falls madly in love with him, he has a battle, he wins, but loses the woman and walks into the sunset. It works every time and I love them!
3. Me...but I suppose one book published and another in the edit phase doesn't count as a series....yet!
All the current best-selling authors keep to a formula if it sells....agents and publishers will insist on it I suppose...though creating a new and separate wheel is a good idea to keep the creative juices flowing. JK Rowling moving on from the Harry Potter books into adult mysteries is a courageous move and she deserves every success, both in sales (not really in doubt) and from a critical audience. Strangely, people like icons to fail!
So keep the mold, keep the round wheel and don't be afraid of being a typecast actor. It pays the rent.
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