Frequency is usually sold, not planned. That is why so many route books are lumpy.
Why it matters
Each frequency creates a rhythm. Monthly accounts return twelve times a year, quarterly four. Mix them without thinking and some weeks carry double the load of others, permanently. The schedule then looks overbooked and underbooked in alternating weeks, and people conclude they need more technicians when what they need is a flatter calendar.
Frequency also drives margin. A quarterly account at a low price with a long drive is a different business from a monthly account next door, even at the same annual revenue.
How you notice it slipping
The same week each month is always the heaviest. New accounts are given a start date based on when they signed rather than where the capacity is. Nobody can say how many visits a given week carries before it arrives.
What to do
Look at committed visits by week across a full quarter, not by month. Where a week is consistently heavy, move start dates rather than adding capacity — a few accounts shifted by one week will usually flatten the whole pattern.