I think it’s more of a, spend some time away seeing many different things until yr local cache forgets you mined it. I’ve never actually timed it myself but my moulds always back whenever I think to check.
You can also stick stuff on em and make Mooould Cows.
I have two farms, fierce mouldy and weyland mouldtani, I hit a bug in liquidators that gave me maxed out nanites so I haven’t been back to them lately but reset my nanites to 300,000 using cross save/pc save editor recently so they’ll see me return eventually.