Are the Dandelions in the fermenter or are you just fermenting the juice?
If on the flowers (fruit) it should only be fermented for 3-5 days of actual fermentation then racked off the fruit or the fruit bag removed. Secondary ferment can sit on the lees until clear but recipes say to rack off the sediment at 30 day increments if over lee thickness is over 1/4". Fine lees can be left longer, up to 3 months. Some wines are left on fine lees until bottling time for the added complexity the lees provide to the wine. This is called "sur lies".