I think the majority of people put 1000 to 1500 mile on a Cobra per year, unless you are fortunate to live in an area with really good weather. That being said, you will probably get at least 5 years out of a solid roller cam before you have to worry about the lifters going bad. With a good rocker arm setup you should only have to set the valves 1 to 2 times per year.
I went with the solid roller setup in my car. I built my own motor, 427 iron block with 4.25 stroke steel crank. I went with Dove's modified high riser heads (Glidden version), a custom Dove tunnelwedge intake (it fits under the hood) and a comp cam with pressure oiled lifters. I had the Kirkhams make up a set of headers to match up with the exhaust port, and had to get a special set of rockers with extra offset to clear the intake ports. At 10.5 to 1 comp, it runs great on pump gas. It will idle below 800 RPM (but I set it at 1100 RPM to better
oil the rollers). It pulls like a freight train from idle until I run out of balls. My motor peaked at 6800 RPM. On a conservative Dyno it made 650+ foot pounds of torque and 750+ HP. So far, no regrets.
Paul