We recommend that you have your watch's water resistance checked every year (partial service with movement check).
Just as with any other precision instrument, a watch needs to be maintained regularly to ensure faultless performance. We are not able to specify a frequency for such operations, as this depends entirely on the model, the climate and the care with which each watch is looked after. Generally speaking, a watch should be serviced every 4-5 years, depending on the conditions under which it is worn.
We recommend that you contact an approved Longines service centre. It alone will have the tooling and equipment required to carry out this work and perform the necessary checks to a professional standard. In addition, only Longines specialists can guarantee that their work will meet the strict quality standards applied and imposed by Longines.