Do we have to take the ongoing arrangement?

Handover is real: the system is documented in plain language, the team runs it without me before I step back, and nothing about the build assumes a retainer behind it. The monthly arrangement exists because systems drift, not because the system needs me inside it. People leave, jobs change shape, the tools update themselves, and six months of small unnoticed changes can undo a good build; the check catches that drift while each piece is still one conversation. Some firms take it for the life of a job, some run the first few months and then carry it themselves, some never take it at all, and all three are using it as intended. It is a fixed monthly amount, agreed in writing, and it stops at the end of any month with nothing further owed, so the decision is never a trap either way.