How often do nail extensions need to be "topped up"

It depends really on how fast your natural nail grows, but on average I would say aroud 2-3 weeks and you should go back for your infill, then after that another few weeks and you will be ready for a rebalance, your smile line will need to be repositioned as you wil be able to see your own natural smile line due to the regrowth, the whole enhancement will be filed and a new smile line applied. This is different of course if you are having one colour, or maybe had something fancy done with art, glitters, fimo canes or something, hth x