That may be the case. I remember reading at the Gen-gas site about an Australian experimenter who attempted to use a generator gas vehicle in day to day use, including a commute of about 60 miles each way (Australia is a LARGE continent!)
He reported about 5000 miles per large scale clean out and refurbish, to include new rings and valves. This with a 1950s era pickup.
It's been a while since I've explored the site but much can be seen on this subject generally at
http://www.gengas.se/welcome_to_www_gengas_se.htm
The old Mother Earth News also had a lot to say on this subject - ALWAYS in the most glowing terms (as befits their enthusiasm and marketing.) They were always prone to overspeak in their agenda which included at least two generator gas vehicles (One a Ford F150 pickup IIRC.) I see they're still beating this drum
http://www.motherearthnews.com/green-transportation/wood-gas-zm0z12amzroc.aspx#axzz2T5aOmY6R
Perhaps a lot of the issues have been overcome? One hopes.
Joe K