Since your style of RVing is just weekends and not far from home, I don't think you need to join any kind of club. However, if your 62+ and enjoy national parks, national forests or Corp of Engineers, definitely get your Senior Pass for 1/2 off on camping.
If you mainly do RV parks, Good Sam might work for you. Passport America is much better but many parks have limitations on weekends. We used it a lot but were flexible and could use it during the prime times. We didn't do KOAs - too expensive.
We tried FMCA but found we really got nothing out of it. Their campground discounts are the same as Good Sam. Their magazine is a joke - very few good articles. We got our Michilin motorhome tires cheaper by shopping around and ended up in Oregon - no sales tax.
We also belonged to Escapees RV Club which was our top choice. The magazine was packed with articles written by RVers and very little advertising.
It just depends on how you RV.