Pre holiday prep - how far in advance

I am going on holiday in August. My partner swears by using a tanning bed as prep to reduce burning. I burn like a peach so I’m going to give it a go. But when should I start? I am going to speak to my local tanner, but I want to go with a bit of knowledge so that they don’t just say ‘start now’ in order to get my cash. Any tips would be appreciated.