All my baskets are made from seasoned willow so there should be very little shrinkage or movement. All my baskets will benefit from being taken once a year and immersed in water for several (up to 24) hours. For those who live in a climate with rain then leaving them out for a day of rain would achieve this. It is essential that the baskets are allowed to dry thoroughly afterwards, if a basket has been lined it should be pulled out (while still been left stitched in) while this is done. Also if some mould should come on a basket from fruit or whatever wash off with warm water and allow dry.
This soaking is not essential. It's main purpose is to tighten up all the weaves and to wash off dust so if soaking is inconvenient it is best to simply wipe the surface with a well dampened cloth and gently rub the surface of the basket.
As with all products made from wood it is wise to check for any evidence of wood worm at least once a year. If any woodworm holes are found treat immediately with a wood worm product such as cuprinol low odour wood worm killer.