Regarding this though:
It makes it much harder to be a Wizard who keeps his spell-flinging on the down-low when so many effects are shortened into a tiny lifespan.
Wizards are a pretty powerful class. I think it's unreasonable to expect that you can entirely buff away class weakness. There are some core spells that actually are hour/level durations such as ultravision, protection from alignment and stoneskin that can provide you with perpetual defense. You just won't always be able to carry 200 lbs of stuff or always be invisible or always be able to see invisible things, which is fair. It's part of playing the class and you plan around it. Wizards are like Batman, they're strong as long as they're prepared. And you need to be on top of being prepared.
I can understand mechanically why you would be inclined to reduce the lengths of some of the more utilitarian spells that Wizards/Sorcerers get. I'm not arguing that or even refuting it. Thematically, it makes playing a Wizard/Sorcerer a little more annoying as a whole. On tabletop, you would have - A day, some limited encounters set up by your DM, and time was relevant. You may have ten or twelve hours of supernatural Bull's Strength on your Wizard, but for the sake of story flow that almost never becomes an issue or even closely watched. Whatever events you may be personally partaking in at the speed humans would interact are accounted for, and you will not feel the need to suddenly plop down and cheekily check your shoe or whatever it happens to be, to keep up the arcane facade. It's just there, you're a Wizard. It's what you do.
Here, however, people are still interacting at a similar speed - if not slower due to OOC distractions or slow typing speeds. Only now, time is extremely sensitive. An hour passes in about seven minutes, and you might have about three hours to kill with a standard Bull's Strength or six with an Extended Bull's Strength. It seems to scale with the rest times of various level ranges fairly well. So instead of a smooth, dynamic experience at least moderately akin to Tabletop, you end up with a lot of things falling short and forcing your Wizard to essentially "Memorize his spellbook" every three hours to keep it up. Which I really don't have a clue how to play off except maybe being mentally fatigued and needing a moment to recollect myself -- Because the mechanic it's supposed to represent has been molested from figuring out your spells at dawn and making them last until dusk, to flipping to your arcane cliff notes every three hours because you're extremely bad at what you're doing.
The only big impact I have ever noticed is now my dungeon runs are done on an extremely tight clock and we all have to rest every 2-3 hours on the spot to prevent spells from failing mid-combat. Otherwise, you can just rest it off, always.
tl;dr - I don't disagree with your balance ideas, just every time I see a spell get shortened I cringe because that's another time I have to break the flow of a scene or event, or a dungeon to check my arcane cliffnotes. Even if it's something for the better like Greater Sanctuary turning into Ethereal Jaunt.