What the OP might not be aware (as he is asking these questions) is that at expiry even if the spread ends a few cents ITM and one might assume that everything will be matched out this is not necessarily going to be the case 100% of the time.
Three problems with the above gibberish, as I see it... firstly, you're a moron (angry ol' atticus again). Secondly, the thing was $3.50 (nearly one percent) OTM (risk as valued in the 45P) in the final moments of LTD of the expiring contract. NOT remotely a pick-em scenario, 50/50 proposition or however you wish to portray it. Something less than 30-deltas as I think we can all agree. Some would even say it was fast-approaching ZERO-delta. It's one of those intangibles that isn't model(able) to a great extent.
Thirdly, you accuse me of repeating myself yet bring up points-covered, ad nauseam. Mebbe you should stfu and stick to your knitting, BUT since you continue to bring it up...
To the OP (to reiterate/beat the dead horse): If you "want it all" then you should solve for the costs associated with getting neutral in shares (and holding thru exp) vs. the potential risk of not receiving the auto-ex and assignment on the legs of the bull vert. It seemed a good-risk to me to let it run through expiration. The shares didn't trade more than forty cents in the AH, but of course that's hindsight. IB would not have auto-liquidated it.
Personally, I would've closed it. I suppose I would've held it through exp only if I'd bot it that morning. Your EV changes with the the price you pay and the time you hold (the position).