Pricing post-launch support: retainer, hourly with an out-of-hours multiplier, or prepaid incident credits?

Retainer, but sell availability rather than hours.

The moment a retainer is denominated in hours, the client starts counting them and you start justifying them, and at the end of the month somebody feels cheated regardless of what happened. Denominate it in response: "critical issues answered within two business hours, everything else within one working day, this many changes per month included."

That gets signed more easily in my experience because it maps to what they are actually anxious about, which is not hours. It is being ignored when something breaks.

Hourly with an out-of-hours multiplier is the only one of the three that changes client behaviour, and behaviour is your actual problem.

When 2am costs triple, an astonishing number of 2am problems turn out to be 9am problems. A retainer teaches the opposite lesson: contacting you is free and already paid for, so why wait.

The cost is that hourly is harder to sign and gives you lumpy revenue. Worth it early, less so once you have enough clients that predictability matters more than teaching each one manners.

Whichever model you pick, define "emergency" in the contract with examples on both sides of the line.

Site down, checkout failing, data loss: emergency. Logo is the wrong shade of blue, a report looks odd, someone wants a new field: not, even if it is said in an urgent voice at 11pm.

Ambiguity is what makes unpaid 2am work possible. It is very hard to argue with a list you both signed, and very easy to argue with a feeling about what is reasonable.

Run the margin arithmetic on the roll-over question before you decide anything else, because it is the clause that quietly decides whether this is a business or a hobby.

Hours that do not roll over: you are paid for capacity, unused months are margin, and that margin is what funds the months where everything catches fire. Hours that roll over: you have written a liability onto your own books that gets called in at the worst possible time, usually as "we have banked eighteen hours, we would like a new feature", which is not support at all.

If a client will only sign with roll-over, cap it. Three months maximum, expires after that, stated on the invoice every month so it is never a surprise.

Prepaid incident credits have worked well for me with clients who genuinely need me twice a year and hate monthly commitments. They buy a block, they draw it down, they can see the balance.

Two things make or break it. The expiry is what makes it viable — without it you are holding somebody's deposit indefinitely against work you may not want to be doing by then. And you have to actually enforce the expiry the first time, kindly and early, because if you waive it once it is not a policy any more, it is a negotiation.

Include twelve months of free support in the build price. It wins deals, it costs you almost nothing because most clients never call, and you look generous doing it.