Assuming the analysis was right, the design was good, the delivery spot on, the change preparation, adoption and benefit realisation effective - you might want to ease off a bit.
The months after the months after a solution is successfully delivered are difficult times. A sponsor may have a new initiative to concentrate on, the delivery team has disbanded, and the initial support level (early adoption) might have run out.
This is when an organisation needs to maintain FOCUS - and not let the bad habits return and the benefits decay.
It is vital therefore that operational arrangements are in place to sustain the solution - to adapt it in minor ways to changing needs - but also that the vision is returned to and upon the results of the first benefit reviews - that the next steps in terms of vision and strategy are initiated. Naturally - if the initial change was part of a programme - this is going to happen - but if only a stand-alone project - who's going to take this on?
Which is where a solid Portfolio, Programme and Project Office (and Head of) comes in - as the business owner for all the change, and the key thought lead, energy source and conscience for the client organisation.
This person may exist, may need to be interim, or will need to be developed - but they are needed.
If your organisation is too small to develop and maintain expertise internally, then a partnership taking a service level to inject this may be the right approach.