Interesting points re the doors.
I once took off from a busy international airport in an early PA-34 (Seneca I). Ordinarily I'd give the doors in most a/c a thump with my fist after closing, just to check they're truly closed, but in this case the only passenger was a rated pilot...
I watched him close the door, then a little later, before powering up, asked him if he was closed and locked. Yes! he said, and gave it a half-hearted lean.
Shortly after, on the climb out, the door popped open. I don't recall now whether it was just at the top but, while it was noisy, I didn't consider it dangerous and following a quick attempt to close it (nope, it wouldn't) I elected to carry on and find a nearby small airfield to land and properly close the door - glaring at the errant passenger in the process.
What I (re) learned from that was to always check the doors with a good push myself if I could, no matter who was in the RH seat.
I was happy with the decision to carry on at the time, and would probably do so again under the same circumstances, but if anyone thinks differently it'd be good to hear from you. FWIW if it had been a quiet aerodrome I'd have just circled back and immediately sorted it out on the ground, but after weighing up the hassle factor in this case vs the likelihood of any real problem we got out of controlled airspace first...