Normally, exterior painting jobs will need to be redone every 5-10 years. Render tends to last longer, wood on the other hand expands and contracts more with changing temperatures which will loosen the paint sooner.
It is best not to put off your exterior painting until the house is badly peeling. When it gets to that condition, it will end up costing you more in preparation time and possibly dry rot repair work.
If however, the property is in a bad condition when you get to it, do yourself a favour – go the extra mile and ensure that thorough surface preparation is done. The idea is to create a sound surface (priming) for the new coats to adhere to. This requires more time but is necessary for the paint job to last.