I actually witnessed a scenario while on vacation visiting a certain shul (to be unnamed) in Florida:
Shabbos shachris, davening starts with around 20 men, at least 15 of them are non-member visitors,
The non-member guests ARE the minyan!! (Except for Rov, Gabbei and three regulars)
The chazon for shachris is a visitor that has a chiyuv.
Yet, lo and behold, at shochen ad a few members trickle in – one has a chiyuv and wants the omud (he will catch up quickly by saying Boruch Sh’Amar. Ashrei, Oz Yoshir…)!
Guess who davens at omud from Shochen Ad – the member chiyuv!
More members wander in after shmonei esrei and they need the limited siddurim, chumashimm, seats and Aliyos.
These late attending members demand their seats, siddurim, chumashim and bump the chiyuvim for aliyos of the visitors that MADE THE MINYAN!
I felt a sense of injustice – if you want your “rights” as a member, COME ON TIME!
Do late coming members get their seats reserved indefinitely – to remain empty, until they show up?
At what point does the “reservation” expire and the seat is freed up?
I think of “stand by” at the airlines, when a reserved seat remains empty, the stand-by passenger gets it just before take-off.
When is “take-off” in shul davening? (Hodu, Boruch sh’amar, shochen ad, kriya, kiddush)