Upmarket Scandinavian windows and aluminium/timber composite frames offer the best performance. If you have the budget, bespoke oak frames left natural or with an oil finish are very durable and attractive. Stained softwood frames and normal hardwoods need to be refinished every three to five years to be kept in good condition, although softwoods are cheaper. There are many high-quality softwood windows available, most guaranteed for 30 years against rot provided they are decorated within a short period of leaving the factory (although factory part-finishing is the best option) and regularly redecorated in their lifetime. How often you need to redecorate will depend on the paint or stain you use.