you have to consider materials used when updating to a solid lifter outfit as well. Spring pressures, RPM and load opposed on the valve train. These are the reasons why the solid lifter applications in racing platforms need to be tended to on a semi regular basis (15-20K miles). On economical (passenger) vehicles like your 240 and others they aren't designed to see high load/stress which is why they last a lot longer. A properly setup solid setup is going to see a lot of stress and with that wear and so forth. Its a pure trade off but the good in it all is that you gain a lot in a few key areas of the engine.
We have to realize that when we start to adopt this new valve train setup which is by far better than a hydraulic setup for racing applications that the abuse factor and overall standing of the car in way of its health and consistency are soley dependent on how well the engine is kept up and built.
