Depends on where the mags actually go to. For example we also send our mags to a specific market segment that regularly contracts for helicopters and we have a couple of advertisers that like to keep their name in front of these people.
Bottom line it depends on what market segment you are targeting. If you are an ag operator then yes direct mail is best. If you are a corporate operator then maybe a mix of ads and direct mail and if you are a supplier to oil n gas industry etc then sometimes adverts do make a difference. Its not about getting a return straight away on the ad spend, its about creating that brand awareness.
Ned