At ASPI Strategist is an excellent article by Marcus Hellyer "The compounding risk in Australia’s transition to new submarines" of February 6, 2020.
Hellyer raises many interesting questions including: why Australia didn't build a "Son of Collins" and why Saab (which acquired Collins builder Kockums) wasn’t invited to participate in the 2015-2016 competitive evaluation process (CEP). Here is a small part of Hellyer's article:
"...[Australia's Department of] Defence has also started to reveal the scope of the life-of-type extension (LOTE) program in the 2020s] see here (page 31) and here (pages 17–22). In addition to all the usual maintenance and obsolescence management of a full-cycle docking, Defence wants to replace the Collins’ main motor, diesel generators, and electrical conversion and distribution system with new hardware made by the suppliers for the future submarine.