Intended as a reply to Matt of course...

I suggest a multi-part approach. It's nice to go for walk outside without being in total darkness. There are times for total darkness, but a neighborhood walk is not such an occasion, IMO.

To hit this first point I suggest low-wattage compacts or similar used in a couple of outside porch fixtures (or whatever fixtures your parents have outside that serve the purpose of a porch light).

Replace the switch inside with an integrated timer switch (from Lutron for instance). These are available at Home Depot, Lowes etc... Get one that's easy to operate manually as well as being programmed. They have some in a Decora style with an easy-ish to read LCD indicating the timer settings. Set the timer to turn the lights on when it gets dark and off sometime after that. Maybe when neighbors (or your parents) are not likely to be outside any longer. Let's say 11pm.

That's all about convenience and curb-appeal. It won't really do much to discourage a thief. At least not a real thief.

To discourage would-be opportunists and vandals, install motion activated spot-lights with a switched override. This will allow the spots to come on when they sense motion, but also allow your parents to flick them on using the switch. You will have to run new wiring for this if you don't already have a dedicated branch for a spot.

A professional will probably look for the easiest targets, but don't be fooled into thinking that any lighting measures or even car alarms can foil someone who is determined and knows what they're doing.

I do think those recommendations go a long way for peace of mind though, as well as offering some usable convenience factors.