Subjects taking valacyclovir (Valtrex), as compared to acyclovir (Zovirax), or placebo (no tretament) reported adverse events similar in nature and incidence. The total daily exposure to valacyclovir and the nature, severity, or frequency of the most common adverse events did not appear to be related. The most frequent adverse events among immunocompetent patients (individuals with a normal immune system) receiving valacyclovir or acyclovir were headache, infectious illness (e.g., influenza, common cold, rhinitis, sinusitis), and nausea. But it is wise to do regular blood tests, say every 3 months, to check on your basic liver (liver enzymes ALT and AST) and kidney (BUN, creatinine) functions to ensure that no injury has occurred secondary to long-term use.
It is important that you recognize possible preventable triggers of herpes reactivation; so for instance if sun exposure stimulates a re-infection, make sure you avoid sun exposure (as much as possible) and that you always apply sunscreen. You also need to limit personal contact when the lesions are active, and be very rigorous with hygiene. You are advised to consult a dermatologist - maybe you can get good results with mere topical antiviral applications (like acyclovir or penciclovir creams).