The longer this goes on, the more it looks like an absolute madhouse with a tory government spinning dangerously out of control. It also lets them say 'we gave him a chance to get a deal before stepping in.'
Boris is in an impossible situation; half the polls say he's comfortable (ipsos yougov) and has the brexiteers in the bag, the other half say he's a bit screwed. Usually in these cases you plan for the worst case - if he's screwed he would go for more 'moderate' votes to bring it home, however he actually can't do that in this instance as anything he does to allay fears on that side, push the other away. Electorally these weeks of chaos play perfectly for the opposition. It's why the tories are trying to goad them so badly.
I understand there’s associated benefits with waiting, but there’s also disadvantages (the timetable for starters) which for me heavily outweigh them. I think you’re placing way too much stock in our politicians if you think they’ve got this all planned and sussed out and are merely waiting to inflict as much damage on the Tories as possible.
Whatever plan they have in mind (if they even have one) it could be upended by the independent actors in this, the Govt and the EU. The less time there is to react to unforeseen circumstances, the less likely it is that their plan works out.