To be honest the reason this wasn’t done for a while was mainly because the setting was non-obviously named, but I’ve finally researched what it’s called. You should be able to edit reactions for up to a year now.
The limit can’t exactly be disabled, but I feel like if you’re going back over a year later to change a reaction to something you should probably be thinking about better ways to spend your time other than this forum 
Also, I did make ‘em desaturated because I agree lol: