How often do you redecorate?

We (my husband and I) are currently redecorating our spare bedrooms. In my husbands opinion they do not really need doing because since the children flew the nest they have hardly been used.  However after a bit of nagging he has given in as he would rather decorate in Winter than wasting caravanning time in Summer.

Our neighbours have currently got decorators in again and he was talking to the lady of the house who said "yes we are decorating our kitchen as it has not been  decorated since it was decorated when we moved in 18 months ago!

They, like us have no pets so 18 month intervals seems excessive to me. What do you think?