How long does it really take for phlebitis to go away ?

Depends: Very good question . It depends on nature and extend and site of phlebitis. Generally non infected phlebitis go quickly if not on joints. Larger phlebitis may take longer time. Local warm compression , elevation of extremities and anti inflammatory agents always helpful. If suppurations ( infection) than may take prolonged time to heal and may cause complication.

Variable: As dr. Vasa said, it depends on a number of things. Fortunately, infection is rare. The biggest problem is inflammation. So anti-inflammatory medicines and compression stockings are very helpful. Leg elevation might make you more comfortable but it doesn't make the problem go away any sooner. Ice and/or heat can also help the discomfort. Resolution depends on the length of vein involved.