Cleaning & resealing imprinted concrete is normally required every three to five years, otherwise it is relatively maintenance free.
How often your pattern imprinted concrete driveway or patio area will need to be done will depend on the usage and exposure to bad weather.
When your pattern imprinted concrete was initially installed, the imprinted concrete slab is coloured and hardened and then should have been sealed with a solvent based acrylic sealant.
Water based acrylic sealants should not be used on pattern imprinted concrete, neither at the original installation stage nor as part of a refurbishment exercise. The resin rich solvent based acrylic sealant becomes a sacrificial layer to protect the concrete below and as it starts to wear thin the concrete will look dirty and dull. The concrete will look as though it is starting to lose its colour.
As long as the original work was of good quality, with the correctly prescribed type of concrete, colour surface hardener liberally applied and any excess antique release agent properly washed off, the process of cleaning & resealing imprinted concrete is a relatively simple one.
If however the surface appears patchy due to too much antique release agent being left on prior to it being sealed, problems with the original installation may need to be remedied prior cleaning & resealing imprinted concrete.