When considering nail polish, it is not advised to keep nail polish on year-round without any breaks. These periods of rest and recovery can help the nails and surrounding cuticle recover from the harsh chemicals within polishes that can also discolor the nail from color pigments.
Traditional polishes are Polymers dissolved in a solvent. This can cause drying and delaminating effects to the nails. This delaminating can create small pockets for moisture and increase the possibility for infections such as fungus, yeast or bacteria. 
Polish manufacturing of cosmetics are now beginning to produce nontoxic polishes that are free of damaging substances, such as formaldehyde, formaldehyde resin, taluene, dibutyl phthalate, as well as camphor and other toxic chemicals. These chemicals cannot only be absorbed locally but systematically may have an effect on a person’s health.
The new gel polishes last longer, but the hardening process uses UV-A light for hardening, which has been documented to cause cellular damage and aging. The removal of this gel polymer requires aggressive grinding for removal and can also thin the nails.
Powder dip polishes do not require UV for drying, but do require aggressive grinding for removal, thus thinning the nails. This type of polish uses a communal powder which can increase the risk of transmitting infections between customers.
Given all the options out there for polishes, keep in mind the nails need to breathe and should have breaks from polishes in order to recover from the chemical and physical assaults.
