AFAIK the oleos should show approximately 11cm of the fescalised portion of the oleo under normal static load. If you load up the aircraft with fuel and passengers, it may well end up showing slightly less than that and with a sticky seal, it could act as you described. In the end, you have to be happy that the aircraft is safe for you to take up into the air, so your decision to leave it on the ground is always a good one. Somewhat older Pipers and Cessnas often have individual traits and issues that you may have to get used to. Have someone knowledgable check the aircraft and if it is safe, have them explain to you what the limits are so that you are able to judge the condition by yourself the next time.