There are two points to feeding a starter. One is to get enough
starter to complete one's recipe and still have some left over to
continue the sourdough process. The other is to have a starter of
known vitality. Most of the sourdough dropouts, as I call them in my
sourdough cookbook, don't get their starter to a known state, and one
time their bread rises too quickly, and the next it doesn't rise at
all. Most hobbyists have starters that are at the ragged edge of
death. The uncertainly compared to using yeast makes them give it up.
As I told my employees, it takes a consistent process to produce a
consistent product. Part of that is having a starter that is
reliable and consistent.
When baking commercially, I prepared the amount of starter I needed
for each day's bake with little or no waste. However, I started
feeding that starter about 7 days in advance. I'd start with a gram
or so and over the next 7 days feed it up to the 30 kilograms or so
that I needed. The controlled feeding regimen provided me with the
quantity and quality of starter I needed. At home, I don't feed my
starters that long. I feed them for about 3 days before using them.
When I feed my storage starter, I tolerate the waste because the goal
is to make sure I have a very healthy starter in my
refrigerator. One that will revive well and work well. And I do use
the excess to bake things.
Mike