Evening before check in has been offered for many years so after 6pm you can drop bags for any flight up to I think 8am the next day. Thats officially supported and works on connecting flights on tickets issues by other airlines

There is a hard stop somewhere in the check in system itself, Dublin/UK/NL check in is 'live' so a lot more flexible, this won't work at outstations elsewhere as they have to get the manifest down and this only happens after online check in is locked.