A probate judge designated to be full-time pursuant to RSA 491-A:4, IV shall not be permitted to engage in the practice of law to any degree. Full-time probate judges shall receive the salary specified in RSA 491-A:1. Full-time judges designated pursuant to RSA 491-A:4, IV shall assist the probate courts in the other counties whenever a probate judge in such other county is disqualified, disabled, or otherwise unable to sit.