I like your plan of testing LEGO bricks[1] from different eras, but I would recommend you use the same rotary mechanism for all the tests. If you change the mechanism to a linear one, you won't be able to compare with confidence the first (rotary) test with any follow-on linear actuator tests.
OTOH, if you repeat the (rotary) 70's era test with the linear actuator, that would be interesting estimate of whether a rotary actuation is better or worse for the brick longevity. Of course, you will still have a sample size of one, so your confidence interval will be meaningless. I can see this turning into a lifelong obsession... ;-)
Once I have a new test machine that his much faster I will indeed retest all the eras (with multiple tests per era). Of course this time I plan to build a real sound proofing system around it. This last machine was really annoying.
OTOH, if you repeat the (rotary) 70's era test with the linear actuator, that would be interesting estimate of whether a rotary actuation is better or worse for the brick longevity. Of course, you will still have a sample size of one, so your confidence interval will be meaningless. I can see this turning into a lifelong obsession... ;-)
[1] http://aboutus.lego.com/en-us/legal-notice/fair-play/