And yes, these negotiations go on for years and years. Which is why we need to get started. And stop blaming everyone else. Get on with it.
These don't. These have a guillotine at two years, at which point we have to take whatever's on offer or fuck off, unless all 27 member states agree to extend the negotiations. We are going to need every second of those two years to get the best possible deal, so we need to have our ducks in a row before we pull the trigger. (Mixed metaphor alert.)
The Cameron government does not have a mandate to set the negotiating strategy that will bind his successor, that must rightly wait for his replacement.