The problem with using lighter sockets for power for external equipment is that in pushing the plug into the lighter-s socket usually damages the clasp located at the bottom which determines how long the lighter is on before it pops-up. The clasp gets spread slightly causing shorter lighter warm-up time,..not a problem if you dont allow smoking in the car.
The other problem are thin straught cut-outs in the socket's wall. Some plugs have narrow earthing springs which snap out into these cut-outs, effectively locking the plug in the socket. To withdraw, requires a lot of force which usually breaks the bakelite plug.
High quality plugs, designed with wider earthing contacts and a narrower end, are the best way out of these problems.
Jason