Tree in June (Dirty Window Version)

I photographed this through a closed upstairs window. People worry over dirty lenses. I am one of them. I puff off the dust with a blower brush. I wipe carefully with a soft cloth. Do you think there is any need?
Photographed with a Nikkor 28mm f/2 AI lens made in Japan c.1981 on a Nikon D2Xs. I had the camera in high speed crop mode, making the effective field of view equivalent to 56mm in full frame terms.