An exterior paint job using the Dulux Weathershield System or similar high quality paint such as Sandtex should last 7-8 years or longer; the assumption being that preparation has been thorough.
if you are likely to leave it longer between paint jobs, go for a two undercoat and one gloss coat, finish, or a one undercoat and two gloss finish. The former will give you more microns or thickness, whereas a one undercoat and two gloss will give a tougher surface.
The extra cost of an additional coat is not one third more but more likely less than 10% and a less percentile again if scaffolding included in overall cost-so well worth considering.
In any case, to give comparison, either a two coat or three coat finish will likely last longer than the next government.
But it’s mid October now so while it’s not too late to paint, it probably is too late to book a job this year as any decent painter has a few weeks lead in time. Get a quote anyway because if your are thinking of painting in early spring or soon as the days become longer again you will get a good before-the-summer-rush price.
Find a painter who shows an interest in your property other than just a paint job. Someone who cares about other maintenance aspects such as gutters, places of needed brick repointing, slipped roof slates and areas of timber that show a liklihhod of rot.
If there’s much height to your property you will need a scaffold to get a thorough job. Make the most of the scaffold while it’s up and have the roof checked and the gutters checked for leaks and correct fall.
I could go on with tips and already have as you can find in this website but please feel free to call me for sound advice and a cost and hassle free quotation.