I did all mine in 3 weeks, just went at it full time and got them out the way.
I am very pleased for you, but it hardly answers the question.
From the first pass you have 18 months to complete them all. After that they all remain valid for 12 months from the date of the final pass. If any time out then they must be retaken.
But remember, if you take them all quickly (as MikeCR suggests) and take a longer time to do your flight course, then you may have your exams expire before you take your PPL test, requiring a retake.
The best thing is to plan your flying and exams to run alongside each other. All the info you need is in LASORS, which you can get from
www.caa.co.uk