Tricky. But you've lived with the light for 2 years. Have you noticed this kind of flicker when the battery is just about done? Does your battery level indicate a full charge or not? If you are getting a green full charge indication and the light is flickering, it isn't the battery. If the battery was dodgy you would be getting partial or no charge indication even though you have had the battery freshly charged.

Has the light ever been dropped or mishandled? Anything rattle when you shake it? Personally I would take advantage of an opportunity to try something different if I did decide to get another light. Might I recommend a MagicShine from Action Led? Similar price. Similar light output. You may become a convert.