Visiting home country when temporary resident

My partner is applying to be on an FLR(M) visa as we've just got married but is wanting to visit his family at some point in the next year. Does anyone know if there are any restrictions or issues with returning home for a few weeks? More specifically he wants to go for six weeks, but I've picked up from others that if it is longer than 30 days that causes issues with the UKVI and applying for the next FLR(M) at the two and a half year mark. Any ideas?

He's free to travel and an absence of several weeks won't be a problem. He needs to ensure that in the 12 months prior to applying for British Citzienship he isn't outside of the UK for more than 90 days.

Awesome, thanks for you help!