There's a mathematically optimal number of times to go to the bank each month
Holding cash costs you the interest you'd have earned leaving it invested, but withdrawing money every time you need a little costs time and fees. William Baumol in 1952 and James Tobin in 1956 independently worked out the formula for the withdrawal size that minimizes the combined cost of both, balancing lost interest against the hassle of frequent bank trips. The same logic now underlies how firms set optimal inventory levels and how central banks model the public's demand for money.