Jon, Id agree with webby about how long things last. Peeps have had a summer of bocking, so 3 months of summer bocking is gonna be v different to the next 3 months, when things are gonna get colder and wetter and windier and the nites longer.
So I tend to talk about 'hours of use' . I kind of reccon simple bocking, no gym or travelling expences, is about 50-70p an hour before new money needs to be spent ( this includes cost of pads). This is normally hooves, tho for some it may be sooner.
To extend the foot plate, glue or bolt on a piece of 5ply or similar to footplate.
To do flips ID say try and hook up with a group t5hat have experienced bockers and a gym. You can see the list of clubs about, are you near any?