How often do i need to get fillers (Juvederm ultra) so they last at least a year or so, is this possible?

Hi, having top-ups around this time is not unexpected, especially with the part of the body involved. Some people can also breakdown the fillers faster than others. 
There are different products available. Some might be longer lasting that Juvederm Ultra.
I suggest you consult with your cosmetic injector and they can discuss the available options with yourself.
All the best.

Due to the movement of the lips, filler tends to break down faster in this area than other areas of the face.  Many patients require to have touch ups around 4-6 months after initial injection.  There are different types of filler on the market and you may notice different periods of longevity depending on filler selection.

After repeated injections, the duration of the lip fillers does gradually lengthen. It is the results of an accumulation of the filler and collagen creation. However, once a year is probably not possible. There is too much mobility around the mouth which in turn leads to faster breakdown of the HA filler than is areas of less mobility.

Thanks for your questions regarding fillers. Not all fillers are created the same. There are variations based on content or type of filler, how thick or cross-linked the filler is, and if there is anything else added, such as calcium hydroxyapatite. Most people who get filler, will find it needs small 'top-ups' at around 4-6 months. There is no permanency to juvederm or hyaluronic acid (HA). HA doesn't promote new collagen formation to make them bigger permanently. The scar tissue from the needle should be minimal/negligable unless there are multiple repeated injuries in the exact same area. HA should not cause pigment loss under normal use. In some cases, such as with infection, this can cause abnormal pigmentation due to the secondary effects of the infection.
I hope this helps!