As far as cost cutting within rolling stock maintenance, periodicity extensions - the suggested example of 28 day checks pushed to 30 days - are unlikely to render any savings. Firstly because of the cost of doing the supporting work to risk assess, condition assess, review, approve/attestation, implement etc. is unlikely to be offset by any, if at all, cost savings. As a consultant I specialised in maintenance deferral and extensions and these were rarely, if ever, done to render a direct cost saving in op ex; they were done to increase train availability or to push a planned overhaul past a franchise date or push a whole round of overhauls past a fleet's disposal date. Secondly, the only real saving you can make on level 1-4 running maintenance is to be able to reduce head count, and you've got to be making huge reductions in the amount of maintenance to do that.
I had a brake pad manufacturer's rep try to tell me that using his brake pads would reduce my maintenance costs. "How?" I asked him. "Because you will be changing fewer pads per exam because they last longer" he says. "Ok, I say. Your pads are more expensive than our current ones so £ per mm of pad material they don't give a saving". "Yes" he says "but you will be changing fewer pads per exam". "But that's not a cost saving" I say. "Yes it is" he says. So I get out the org chart for the maintenance teams and point to it and say "who can I sack because we're using your pads?". Answer? No one....