Baron Buff Does Not Need To Last Longer

Why does barons buff duration need to last longer? According to this it lasts longer because it will make you want to contest it more in the late game. Lets put this into perspective, Baron spawns at 20 minutes. Elder dragon spawns at 35 minutes. Baron is being buffed for literally no reason until Elder dragon spawns. And then think, how many games do you have last to 35 minutes where one team isn't completely dominating the game to where you won't be able to contest it. Can barons buff at least scale with what time it was taken at?

Example: A 20 minute baron will last for 1:45 while a 30 minute baron will last 2:15