I can offer my experience of a change between 1 and 2 hours. I decided to move to a different set of flights the following day, as is permitted with a change of 61+ minutes.

I called in and the agent was not aware of this policy. After a good amount of time on hold, they conceded this was within policy but then claimed they could barely see any available flights. Ended the call politely.

Went to the live chat and the agent promptly re-booked the flights within a few minutes.