We do this for our maintenance retainers... after our sites go live, we continue to provide technical and marketing services on a monthly basis. Pre-paid retainers secure a lower billing rate.
So far, it hasn't been a good idea to start out that way, even from our perspective. The problem with "projects" is that there are usually requirements on both sides, and payment + delivery keep things urgent for both sides. I hate projects that go on forever because the client can't produce things they need to or respond in a definitive manner. Holding the deliverable back is a pretty impactful negative consequence (or: motivation).
We are exploring an "agency of record" start-up engagement where the retainer plus phases may be the way to go. But it's less of a project with deliverables than agency-of-record time and effort.
So far, it hasn't been a good idea to start out that way, even from our perspective. The problem with "projects" is that there are usually requirements on both sides, and payment + delivery keep things urgent for both sides. I hate projects that go on forever because the client can't produce things they need to or respond in a definitive manner. Holding the deliverable back is a pretty impactful negative consequence (or: motivation).
We are exploring an "agency of record" start-up engagement where the retainer plus phases may be the way to go. But it's less of a project with deliverables than agency-of-record time and effort.