Hello from JustAnswer.
Stopping dialysis is dependent upon the clinical situation, not any specific time.
If there is a type of kidney dysfunction that can improve with time or correction of the underlying cause of the kidney dysfunction, then dialysis can be stopped whenever the kidney function is improving. In your case, if the kidney dysfunction is due to the lithium and the lithium cannot be stopped, then there may not be a point in time when kidney function improves. However, if the lithium can be stopped and the kidney function improves, then the dialysis can be stopped once the kidney function improves. Since it has been a year and a half, there is no certainty that kidney function will improve, but if it does improve then dialysis can be stopped.
It also would be appropriate to stop dialysis once a kidney transplantation occurs. However, it is not as simple as finding someone willing to donate a kidney. The donor needs to match you, and the likelihood that any specific person will be a match is low. Since family members share many genes, the likelihood that a family member will be a match is better, but the likelihood of a friend being a match is low. The method for finding a match is to get on a transplantation list, and when a donor kidney becomes available, they will find the person on the list that matches the donor.
It is impossible to predict how long you could live after getting off dialysis, particularly if the kidney function has any improvement if you are able to get off lithium.
Have you discussed getting off lithium with your doctor?
Have you discussed with your Kidney doctor (Nephrologist) about getting back on the transplantation list if the lithium can be stopped?