The .ohms on both the coil units and the built in ohm readers are +/- .1 ohms usually, combined with wattage adjustment, coil units varying in quality and output, along with them getting gunked up if you don't change them regularly, plus your vaping style has changed if this was your first MVP setup I would guess.
It's hard to say but if I had to bet, I would guess that it's more like the above variables than it is the battery. Now it's possible that it's the battery, and you could have it replaced if you wanted to and it needs it, there's lots of people that would replace the battery and the 510 connection for you at the same time while they were digging in, if that was something you wanted to do.
You could always spend $30 or $38 or whatever the new MVP costs and swap the batteries and then you'll have a lot of spare parts, and a new battery on the anniversary present without losing the centimental value. I think I'd roll with it like it is and see if you see it rapidly degrading or not, and if it charges like normal. Maybe even leave it charging longer than just until the green light comes on, or possibly charge it, use it a few minutes and plug it back up to top it off.
Usually when these batteries go bad though, they go bad completely. Like it will die, when you go to charge it or take a puff the lights are wonky as hell and wont charge or wont fire, something like that. With what you're describing, I'm thinking everythings probably fine.