CCTV maintenance contracts are usually based on one visit per annum and would include cleaning the external housings and lenses, checking and adjusting back focus as necessary on the older systems, cleaning and greasing pan & tilt heads, checking and making good any cable defects, test IR lamps, check brackets and mountings for rust or corrosion etc.
Routine maintenance on CCTV systems is important if you want to produce good quality images for recognition and prosecution purposes.
Many people spend a lot of money on having a system installed only to find when they need it most the images are unusable due to lack of or poor maintenance.