From the New Hampshire Department of Labor official website.
How long is my claim open?
Medical bills related to your injury remain the responsibility of the carrier as long as treatment is required. There are certain time limits for indemnity benefits depending on the circumstances of the case. See RSA 281-A:31.
How soon does Workers' Compensation start?
Workers' Compensation starts on the fourth day of disability (subject to a three day period). The waiting period is waived if the disability continues for 14 days or longer or if an employee returns to temporary alternative employment within five days.