Permitted work - what happens, coming to an end

I am on employment and support allowance and have been doing permitted work at the higher rate, over £20 a week, more than 3 hours a week. Under the rules this can only be done for 52 weeks then you have to wait another 52 weeks before starting again.

I do not want to loose my job but am unable to hold down a part time job, due to my health , which would be a minimum of 16 hours a week and mean trying to claim the disabled part of working tax credits.

Does anyone know if the above is correct, Thankyou