Mode B — Fridge (Bake Once a Week or Less) ⭐ Recommended for most people

Best if: you bake every 1–2 weeks.

This is what almost every experienced home baker does. Here's the exact protocol:

Switch to a smaller working starter — you don't need 75 g sitting around. Going forward, maintain just 25–50 g as your "mother."
Get a clean glass jar with a tight-fitting (but not gas-locked) lid.
Do a final fresh feed: 25 g starter + 25 g flour + 25 g water. Stir well.
Leave on the counter 2–4 hours until you see active bubbling and rise (not necessary to wait for full peak).
Refrigerate. That's it.

Pull the jar from the fridge. You may see a layer of dark liquid on top called "hooch" — that's alcohol the yeast produced when food ran out. Either pour it off or stir it back in. Both are fine. Hooch is normal and not bad; it just means your starter is hungry.
Discard down to ~25 g (this is your weekly discard — save it in your discard jar if you want).
Feed: 25 g flour + 25 g water. Stir.
Leave on the counter 1–2 hours to wake up (no need to wait for full peak).
Back in the fridge.

That's the entire maintenance commitment. 5 minutes once a week.

When you want to bake:

Two days before bake day: Pull starter from fridge. Discard down to 25 g. Feed (25 g flour + 25 g water). Leave on counter.
12 hours later: Discard down to 25 g. Feed again. Should now be doubling within 6–8 hours — that's your readiness signal.
Bake day: Use it to build your levain (per Nick's recipe). After building the levain, feed your remaining starter one more time, let it rise 1–2 hours on the counter, and put it back in the fridge until next time.

The float test: Drop a small spoonful of starter in a glass of water. Floats = full of gas, ready to bake. Sinks = needs another feed.

Up to 2 weeks without any feeding: completely fine, will revive in 1–2 feedings.
2–4 weeks without feeding: still fine but expect 2–3 feedings to fully revive. Hooch will be substantial.
1–2 months: likely revivable but may need 3–4 feedings over 2–3 days. Pour off hooch first.
3+ months: risky. Can sometimes be saved but quality may suffer. Consider keeping a backup (see Mode C).

A starter can die in the fridge if completely neglected for 5+ months. Don't push it that far without a backup.