One thing we've learnt from developing websites is that familiarity breeds...well, if not contempt, then at least an over familiarity with the design. When this happens, change for the sake of change becomes an attractive proposition.
For this reason once a design is agreed, we find that it is better for a client to see progress only when we are approaching the final stages of the project. The realisation of our efforts stay fresh and the risk of getting mired in expensive change requests is largely reduced.