Some of the older models have a little switch button on the headlight switch that disables the running lights.

You could download PDFs of owner's manuals from Volvo and research what models have this feature and then order a switch or find one at a junk yard - I think that the owner's manual would have a picture so you know what to look for.

a wiring diagram might show you what wire to disconnect to kill this feature.

Personally, I use the running lights and do not mind the extra expense. Light bulbs lose their brightness gradually during their lifetimes partly due to deposits of vaporized metal inside their capsule. A long-lasting bulb will have a long period of diminished brightness.

I suggest that you take a good look at your current bulb output - like lighting a white building from 100 feet (take a picture?) and then try a nice new pair of Silver Stars.

I found that I liked the extra range enough to foot the expense. I keep the old bulbs in the trunk as spares.