Regular painting is the most essential part of making your windows last. We would advise to visually check over the windows annually. Any flaking paint or cracks in paintwork should be rubbed down, sealed and repainted.
Particular attention should be paid to the external of the windows if you have double glazing. The sealed units units will fail if the paint overlap between the timber and the glass is not maintained and water is allowed to get in contact with the edges of the unit.
There are a lot of different paint products on the market, but we would recommend oil based paints as water based products appear less effective in the long run.
Bedrooms, shower rooms and kitchen can have much higher levels of condensation than other rooms. If the moisture is not allowed to escape it will condense on the glass and the moisture will soak into the timbers.
Ensure these rooms are regularly ventilated by opening the windows until the moisture has escaped. This will reduce the intervals between repainting and prevent mould or decay forming.
The sash cord is the only item on a sash window you would regard as a consumable.
Sash cords on all windows will eventually wear out and snap, due to being under constant tension and the friction on the pulley wheels.
The life span of the sash cord is shorter for larger and double glazed windows than on single glazed windows. There is little can do to prevent this apart from keeping the pulley wheels oiled.
It is normally a straight forward job to replace these.
The sand mastic pointing which goes round the exterior of the windows is just sand and linseed oil. It is non setting, as it should move with the windows shrinking and expansion. It will gradually dry out as the oil evaporates. Painting boiled linseed oil on this with a narrow paint brush will prevent this from drying out.
Ironmongery is normally laquered so will need minimal maintenance other than an occasional wipe with a cloth. The pulley wheels are the only moving mechanical item, so a drop of oil every year or so will be sufficient.