_do they keep asking for favors without giving you the feeling that you are still friends?_

Then they disappear until the next time. I do not mind helping others at all! I try to help people as much as I can.

_if they think, for you to be worthy of their friendship requires effort on your part, then they probably weren't good friends to begin with._

This might be the case with me atm. I simply can't afford to manage a perfectly feasible time because of personal reasons. However, I have friends who work around these limitations and still manage to catch up. There are some who do not consider this limitation.