Longest lasting fillers for lips? Can't decide between Juvederm Ultra Plus, Restalyne, and Teosyal Kiss. Advice?

Avoid the runny fillers.  They do not hold where they are placed.  Injectors like them because the lumps and bumps they make fix themselves.  Unfortunately this leads to the impression that the filler is not holding up.  Also these fillers result in general volume that does not respect anatomy.  Product placed in the lip edge will drift causing the dreaded lip shelf.  For this reason, I do not low G prime, high tan delta products like Belotero, Juvederm, or Teosyal.  Restylane is the best of the products in my opinion.  It is a high G prime, low tan delta filler.  It has to be sculpted into place but the treatment stays put and is the best of the fillers for the lip edge.

Lip augmentations with these fillers (Restylane, Juvederm) is a great option to improve the fullness, suppleness and symmetry of the lips. Results can be very natural-looking and will feel very natural. I prefer to use a micro cannula to inject the lips to prevent bruising. Look for a cosmetic dermatologist or plastic surgeon who is an expert in fillers. 
I hope this helps.

Thank you for your question. All the fillers you have mention are good options for lip augmentation. Some common side effects of dermal fillers are bruising and swelling which can take up to 2 weeks to resolve and typically results last 6-12 months. I recommend having a consultation with an expert to determine the best treatment plan for you. Best of Luck!