After time your patio tiles can become stained and dirty and even have weeds growing from within the gaps between the paving slabs. Applying weed killer and performing some minor maintenance will keep the patio area looking in shape as time goes on.
But eventually you will need to get a high powered jet-washer to clean the tiles and the gunk that has gathered in the gaps between the paving slabs over the years. This will give your patio area a new lease of life, but it will also leave some empty gaps between the tiles if you were very intensive.
You may have to re-level the tuft where the edge of the patio paving meets the lawn, if this is the type of garden-patio you have in your garden; this way the lawn to patio is nice and level.
Once you have Jet-washed your patio paving and the area has dried, you should spray some weed killer in the gaps between the tiles and wait for that to dry. Once that has dried you can start putting some sand down and sweeping the sands into the gaps until they have all been filled, thus leaving you with a revitalised patio area for a few or more years to come.