Yep tennis doubles don't need you to be great player. (relatively speaking)
It does not need you to run, run, run like in singles. Points are normally short.
Paes, Bhupathi, Bryan brothers are examples. They are not great singles player but remained very strong for years in doubles.
If you have good hand eye coordination you can play for long in tennis doubles.
Navratilova case was different though - she used to play singles at old age! And also reach finals of grandslam.
Federer is only likely player who can match her in singles. He is still top 2 player at age of almost 34 and fit enough to play 3-4 more years. (May not win grand slams but can continue to play if he wishes)