Painting and filling exterior window cracks

[Twentyfour7]

Hi All

Most years my windows crack at the joints and I sand down, fill with ronseal woodharder and paint with Dulux weathershield

What is the best filler to use to stop this happening please
Any advice greatly appreciated !
Thanks

[119]

Wood is a natural product and will move with temperature changes.

You could rake it out and try a decent caulk but even that will eventually open up.