My 15 Year Old Grandson Has Been Taking Valacyclovir HCL

My 15 year old grandson has been taking Valacyclovir HCL 500 mg 1po qam for the past 2 years for suppression of herpes lesions on his lips and face. It has been very effective and he doesn't want to d/c it as he hates getting the lesions. He hasn't had any noticeable side effects but I am wondering if it is safe for him to continue indefinitely???