The doctor I had a the time of my picc line did not clean it as it should be. That is every time it is used and it must be wrapped so it is not getting wet when taking a shower. Mine got infected and was taken out because of those errors but yes it is up to the doctor as to how long he feels you will need it.
A friend of mine who is a nurse with Lyme, after 3 picc lines that became infected because she was too ill to clean it and her home health nurse didn't, went for a med port. Something put in under the skin. you can swim, shower and not worry about it getting wet. Her doctor only did IV therapy. I know that if I get to that point, I would go with the med port. Something to think about.
Everybody is different, and each doc has different standards they go by. There's no one size fits all.
If you haven't asked your doc how long s/he expects you would have the PICC line, I would do so.