Sharing experience of my return flight to the US:

I was able to select any available seats for free at T-2 for both flights (Spain-LIS + LIS-SFO). I did not attempt to change the seat selection at T-36 this time.

Flight Spain => LIS:
At T-90mins I switched on the app from an aisle seat to a window seat of the same row. Any seat selection on the app was showing as free. However, changing seats for the flight LIS-SFO was still showing as paying, so I did not attempt it.
When checking in my luggage at the counter in Spain, I asked the agent if I could switch my seat for the LIS-SFO flight (remain on the same row but aisle instead of window) and she said the system was requiring her to collect the payment for it, so I declined.

Flight LIS => SFO:
At T-2 exactly all available seats became available for free. I know for a fact this was the cutoff time because 2 mins before that time changing seats still required a payment.

I Just tried today and still worked (23/01/2020).
2 hours before the flight all seats were available.
Flight from Fortaleza to Lisboa.

Hi all, I will be flying VS from HKG to LHR and connect to LIS on TAP. Both flights are in the same PNR and I have a 3-hour layover at LHR. Will I be able to select seat and receive boarding pass for the TAP flight during check-in at HKG? Thx!

Anyone knows why on some fights I am allowed to select my seat from booking, but on some flights I get a message saying the seat map is unavailable? Is it because there may be an aircraft change?

Have a LIS-OPO next week on a ATR and can't select a seat, later on the week I'm doing OPO-LIS-FAO and I'm able to only select the LIS-FAO seats (on an ATR). The rest of the flights seem to be ok.

Ponte Aérea flights (LIS-OPO and vv) weren't eligible for advance seat booking.

Didn't know about that. Thank you! Would it be automatic seat assignment or can be selected during online check in?

Being Gold you'll have no problem in selecting the seats. Usually the ones close to the front are reserved for status pax even in ATRs.

In ATRs you'd want to be able to sit further back - first on - first off.

The ATRs and Embraer's have the economy xtra seats, but is there any advantage in seating on them? They seem to be identical to regular economy ones.

I'm on a quick ATR flight so chose to seat near the back - first on - first off, as you said.

The advantage is that as a rule, unless the flight is full, there'll be less people seating in that area because seating is restricted to status pax. I'd take that over boarding first or deplaning first any day of the week, especially in the current context. And in any case, if you have status, boarding first or last is always your choice, regardless of whether you seat upfront or in the back.

T - 2 - YYZ - LIS Seats were free to choose (Desk lady changed them for us for free T-3)

T- 1 LIS - YYZ - Seats were free to choose (Desk lady refused to change them and said ask the counter people 1 hour before, changed it myself 1hr 5 mins prior)

FNC-LIS T-2 Seats still not free ... T-1.5 Seats free

I flew EWR - LIS on Oct 24th and it seems that their system has changed. The system automatically assigned my partner and I the two middle seats in a row of 4 on the A330. When we were checking in at T-3 I asked the check-in agent if she could move us to a two-seater aisle/window (there were plenty available) but she said that the system wouldn't let her do it without asking for payment. I told not to worry about it, as I could change the seats myself at T-2 (as I've done before), but she told me that that wouldn't work either anymore, and that the only way to change our seats would be to approach the gate agent at exactly T-1 to have the seats changed there. She was right - the app wouldn't let me change our seats at all without paying during the T-2 - T-1 window, however the gate agent did change them at T-1. Not sure if this situation was specific to this flight, or if it's system-wide.

Similar experience on LIS-MAD last week

OPO-FNC and had the same surprise. Seems the trick no longer works. Was asked for payment up to T-1.5 at which time I decided to go through security anyway and just pay for it.