Airbus in their FCOM3, recommend NOT to do any realignment of the IRS's if the residual groundspeed of the 3 IRS's is less than 5kts. If even 1 IRS has a residual groundspeed of 5kts or more, a quick realignment must be made. That is for transit stops.
Also, FCOM3 says " For flights with long segments on which there is no updating of FMGC position with radio navigation (i.e. over the North Atlantic MNPS airspace, especially if the aircraft is not equiped with GPS), perform a complete alignment. For all other flights a quick alignment is sufficient. ADIRS PERFORMANCE MAY BE DEGRADED IF COMPLETE ALIGNMENTS ARE SYSTEMATICALLY PERFORMED.
Hope it helps.