They have no job description or schedule of duties. They can do what they like for as long as they like, subject, of course, to their need to be re-elected.
They normally have the equivalent of a five-year contract with no period of probation nor any individual test of competence. Many young professionals today are on contracts of three years or less with a six-month probationary period.
MPs are interviewed and selected by bodies that do not represent either the people who will receive the service or the body which will pay them.
The reason many MPs work long hours is that they get involved in matters which could be more quickly and effectively dealt with by the officers of local authorities. Often they are engaging in early electioneering. Paying them for this is like paying young graduates for job hunting or polishing up their CVs.
It is not clear whether the 80 hours includes time spent hanging around waiting for the photographer from the Evening Despatch to turn up and snap them pointing at Mr and Mrs Robinson's broken-down wall and/or patches of damp.
I am willing to swop jobs at existing salary levels with any MP at any time, saving my honour.