Break Clause?

Tenancy Types and Management

I'm hoping for a relatively long term tenancy and have a potential tenant who said they wanted to rent the property for 3 years - which would suit me about right. I put 36 months within the tenant application form but a company employee who's job it is to support the applicant with their move has asked if it would be possible to insert a break clause after 12 months as 'a very small minority' of employees maybe asked to move site during their contract. My question is whether there's any point/benefit to such a break clause (if I included it, obviously I'd make it mutual) or if I'm better just reducing to a 12 month AST and rolling onto a periodic tenancy thereafter? Thanks