Eldar may leave their spiritual path and wander as Rangers, where they perfect their powers of invisibility and stealth, but they never truly leave the Eldar who are a people under siege. Many Rangers prove their worth by scouting out new access gateways to the webway, a technology that once linked all of Eldar space, allowing them to travel instantaneously across that distance.
All members of the Eldar, even the most disillusioned ones understand the nature of the Eldar's existence as a people now wandering the universe on Craftworlds, without a planet to call home in a very hostile and dangerous universe.
Utilizing their superior spaceship technologies, the Eldar are able to create and maintain webway access points which Rangers who may need to or want to return, are able to do so. Demonic possession happens far less with the Eldar who are wise to the machinations of the beings of the Warp and avoid them using their designated webway portal technology. A webway connection is a stable one and possession is unlikely for anyone traveling there.
The webway was once a galaxy spanning, sophisticated network of paths though the Immaterium connecting all Eldar no matter how far apart they may have been. With the birth of Slannesh, the shockwaves disrupted the Immaterium and much of the webway. Now with the corruption, destruction or loss of knowledge of much of the webway, any paths though it become more precious and the largest ones become staging areas for the Eldar presence.
Many Rangers use their time away to explore the remnants of the webway mapping it for their people's use.