How quickly do liver alt's alter themselves, what is the optimum re-test period for unknown cause isolated alt raise ?

LFT elevation: I would recheck them in 1 month provided no symptoms are present. By that time any spurious lft elevation would normally clear.

Depends: If you recently had infectious mono, it might be best just repeat when you feel well unless you are super-sick. If discovered incidentally, two weeks after stopping alcohol and all meds is enough time for a drop to be clear if this is the cause. Otherwise, you'll get worked up for viral & autoimmune hepatitis, hemochromatosis, wilson's & perhaps a few others. Stay aerobically active if you can.