I have a tiled shower/tub and the faucets are leaking. Is it better to replace again with washer faucet system or washer less system? I have faucets with washers and they start leaking around every 6=9 months. If washer less is best, can I replace with only a new faucet kit and not plumbing lines and without tearing out wall to make repairs? I must replace regardless, as the plastic tube that covers the stem can not be purchased separately. Please advise and any suggestions? Thanks

washers should last much longer than that. do you change the seats, assuming they are replacable?
as to your question. changing the valve will require access from the other side of the wall if you don't remove any tile.
there are a few different options you can choose but not being there and not knowing what you have for access makes it most difficult to answer more specifically

Are you using well water ? Sometimes sediment in the water will speed up the rate at which the washers go bad.

It is IMPOSSIBLE to answer your question until we know the make and model of faucet you have now. Sometimes it is a simplle matter to upgrade and other times it requires a minor remodel of the wall to do it.