I suffer from insomnia.
Are there any side effects if I take Clonazepam daily as a sleeping aid for long term?
Will I become tolerant to it?
Yes, clonazepam is known to cause tolerance, as well as other side effects (such as dependence) after a prolonged use.
From the medication Summary of Product Characteristics (SmPC):
Prolonged use of benzodiazepines may result in dependence with withdrawal symptoms on cessation of use. [...]
In particular long-term or high-dose treatment, may lead to reversible disorders such as dysarthria, reduced coordination of movements and gait disorder (ataxia), nystagmus and double vision (diplopia).
NHS also states:
Long-term treatment with benzodiazepines isn't usually recommended because they can become less effective over time and some people become dependent upon them.
What's more, Martindale: The Complete Drug Reference doesn't list clonazepam as a medication of choice for insomnia. Nor does NHS article on the treatment of insomnia. Although clonazepam does belong to benzodiazepines, group of medication that is used to treat insomnia, other medicines are recommended. Clonazepam has other indications, such as epilepsy.
Clonazepam, same as other benzodiazepines, is a prescription-only medicine. This means that you shouldn't be able to purchase it, without physician's recommendation. Your physician is able to explain to you the dosage, duration of use, and possible side-effects.
Martindale: The Complete Drug Reference, 2005 The Pharmaceutical Press.