R4 — Commit to a documented input-refresh schedule before shipping any customer-facing calculator; if you won't, don't ship it

Rule: Calculators are software, not signage. Before launching one, the client must own a written input-refresh schedule (quarterly minimum; monthly for rate-sensitive verticals; never for solar/incentive-sensitive). If the client will not commit to upkeep, do not ship the tool — ship a directional range with no embedded rates instead.

Why: Prices and incentives drift; solar incentives change daily (Solar incentives can change daily — unmaintained solar calculators actively mislead); the legal exposure of a stale calculator is real (A detailed online estimate with no reasonable basis can expose you to misrepresentation or negligence — even when labelled "estimate"); a stale calculator silently misleads every visitor. The general data-pipeline maintenance literature confirms this is the dominant lifecycle cost — see [[data-pipeline-maintenance]] topic.

How to apply:

• Refresh schedule written into the project scope, not assumed.
• Calculator owner-of-record on the client side.
• Reminder cadence (calendar invite, monitoring alert) set on launch day.
• If client backs out of upkeep commitment, revert to directional-range variant before launch.