Byrne is no stranger to the early wake-up call, previously stepping in for Maxi -- real name Irene McCoubrey -- when she was fighting a stomach bug last summer.
An RTE spokesman told the Herald today: "Maxi is continuing on extended sick leave, she is better and preparing to return to work.
"Shay Byrne is taking over the Risin' Time slot and Maxi will be coming back to us in a different capacity. She is definitely in our plans, she will have a role in music programming, but it's Shay Byrne who is taking over Risin' Time.
"Maxi has been in that slot for a long time, and getting up at 4am morning in and morning out for such a long period of years, there is only so long one can do it, and she is passing on the baton to Shay."
The Risin' Time slot, which airs from 5.30am to 7am on week days, is regarded as one of the toughest gigs on radio, and Maxi had five alarm clocks at the ready to wake her up in the morning.
She also had an automatic pre-recorded tape of her show which clicked on automatically if she was not in the studio in time.
Maxi suffered from a severe bug last summer, forcing her to take time off and it is believed that she has still been recovering from the illness over the past few months.