for psoriatc arthrits is it important to take medicines if I'm not in pain for the last few months?

You don't mention what medicines you are taking, so this is going to be really general.  When you have arthritis, there are flares and there are good periods.  Often, the good periods are a result of using medication that suppresses or in other ways treat the arthritis.  This means that each you go off the medication, there is a risk of the arthritis flaring again.

When you have a chronic disease that requires taking medication, it's easy to get tired of being dependent on the pills to feel good.  However, changing the way you treat your disease, whether it is changing medications or reducing or going off medication, should only be done in consultation with your doctor.  He or she will be able to take you through the pros and cons of changing your current treatment and answer any questions and concerns you have regarding your medication.

Good luck!

Yes!  It is very important to continue all medications.  The reason being is that these medications actually play a good part in what has made you pain free.  Here is the problem, once you stop taking the medication and the pain comes back, you will have to wait until these medications once again build up in your body to start feeling any relief.  Also, many medications require being weened off and can be harmful to your body if you discontinue them.  If you do decide to discontinue taking your medication, please speak with your doctor first!  Good luck and best wishes!