I've done the same int he past. Booked fairly expensive summer tickets a few months out. Was notified that one flight had a change. By chance the fares had significantly dropped by then, and they had a 20% sale going. So I requested the 120% credits refund and booked the exact same flights for far lower fares. Had enough credits left to purchase Priority boarding and seat selection, and even then still had some left that I used on another flight later that year.

In my case the time change was quite bad, but there were no other carriers operating the route. As it was part of a larger itinerary I had no choice to fly at those new times...but it involved arriving at 2AM or so (rather than 11PM) which was pretty suck-y.