It depends whether any of the nails have come completely off during that time, as obviously they will be newer than the rest. I am speaking as a beauty therapist now and in general, all types of false nails are bad for the natural nail underneath. That being said, people who wear false nails are not happy with their natural nail anyway! There are steps you can take to minimise damage to your natural nail.
1. Don't have the false nails too long. The extra free edge of nail creates a lifting effect on the nail plate underneath and causes damage.
2. Always have your infills done regularly. Any longer than 2 weeks, then you have an uneven balance between the base and tip of the nail, causing pressure and damage.
3. If your false nails have a tendency to lift, then go back to the salon earlier, for maintenence.
Lifting enables water (from washing, showering etc) to get under the false nail, where it can encourage a fungal infection. If you see any yellow/greenish tinge on the nail, then have them removed immediately.
4. Do not pick at the edges of the false nail, no matter how tempting!
5. Always have them removed properly. This means soaking them in acetone (either bought from the chemist, or done in the salon) It takes quite a long time for all the layers to melt and should not be rushed.
I would say a complete whole set should be removed and replaced after 3 months maximum. After removal, you should wait for 1 week before having a new set applied.(If you can wait that long!)
False nails take alot of maintenance and upkeep. After the initial set, the fortnightly infill can cost from �20-�30, so is a committment. Many people budget for the initial set but then begrudge paying for infills and try to spin it out an extra week...then problems begin.
Hope all this helps.