Just as it changed whilst being built, so it changed afterwards. The Romans began to replace the Turf Wall with a stone curtain between the Irthing and Milecastle 54 before the Wall was abandoned in favour of the Antonine Wall, only to resume that process when they subsequently returned to it. That very abandonment and reoccupation led to changes too. Turrets were abandoned and some even demolished, a fort added at Newcastle, and the bridges at Willowford and Chesters (and perhaps Carlisle too) were rebuilt on a grander scale, probably during the latter part of the 2nd century AD (although not necessarily all at the same time).
There was also substantial rebuilding of the curtain wall under Septimius Severus, making up for the deficiencies of the earlier structure and the ravages of time.
Further reading: Breeze and Dobson 2000