It's more to do with size than age with torts. Once they outgrow the closed chamber baby home then they they are usually starting to self soak.
And this is the key. Those of us with adult torts will see our tortoises voluntarily soaking and drinking every day and then we know we don't need to do it so often... and with Sulcatas they get too heavy to lift into a bath!
Daily soaks don't do any harm, so keep going for as long as possible
The occasional (not regular) day off because you are busy won't do any harm though
I soak them daily until they reach 100 grams. At that point I start skipping a day now and then. By 1000 grams 2 or 3 times a week should be enough for most situations.