Is there only so much filler my lips can take? My lips don't seem to be getting any bigger

Thank you for sharing your question.  There is a point in time where the amount of filler placed will preclude additional treatment as the lip tissues can not stretch further.  That said 5mL of JVD UP is a substantial amount for the lips and I would recommend a second opinion or other filler material, such as Voluma/Vollure to see if you have a better volume response. Hope this helps.

As long as it is not volumized to your liking, there is 'room' to place more product in the lips.BestH Karamanoukian MD FACS

Yes, there is only so much filler that the lip tissue can accommodate. But it could also be that this filler isn't the best choice for you. I would suggest that you get a second in person opinion from a really experienced injector. 

Thank you for your question.  This sounds technique dependent - please either discuss with the physician who is injecting you or follow up with a board certified Dermatologist for further evaluation and management.  As well if looking for serious volume consider Voluma in your lips, with a Dermatologist who is familiar injecting Voluma into lips.  Regards, Dr. Matt Elias

You have already had a significant amount of filler in the lips, usually people only need a few mL to augment. After 9 months the fillers may start to dissipate, but usually last 1.5 years. For a more permanent results you can also get fat grafting in your lips. You could also try a different product like Volbella to see if it works better for you.