Are you taking the PPL for afterwards or?
Because that would also affect when you can start your leave, because you wouldn't have to go back til later?

I like the idea of planning for around 36-37 weeks, and if you're too sick or something then leave earlier? But if thats the case, perhaps ask to drop a couple days, or ensure your shift can be covered or youre on lighter duties etc. So if you have to finish suddenly, youre work isnt in trouble.

That way you're not too bored at home for too long either