This in one hand depends on the natural growth of the nail plate, and in the other hand depends on the individually experienced annoyance caused by the downgrowing nails. Generally when the size of downgrowing is about 3-4 mm, it is advised to refill the artificial nail, this happens approximately in 4-5 weeks. But if someone feels the downgrowing too long and annoyed by that, refill is possible more often. This usually happens when we construct longer artificial nail, and downgrowing even after 2-3 weeks can become quite annoying for them.