Context: people used to place hundreds of 1x1 survey flags near other people's bases (often with a script) that would tank their FPS. Only way to remove them (without scripts) requires minimum of two mouse click per flag.
To alleviate this, 5 survey limit per character and eventual decay of survey flags were added. Both probably still have their place (side benefit to the latter is that inaccessible flags will eventually despawn.)
I suggest a number adjustment: 10 flags per character, and flags take one whole RL week to decay (up from ~2 RL days.)