lcoleman...it's not the short drives, per se. It's many short drives and no long ones.
I've been in many threads where that's the issue. Starting draws the most power, and if drivers are constantly making 5-10 trips in a day, each of short duration, the battery will progressively get weaker and weaker.
I don't know what OP drives like, so just putting it out there in case he hasn't been on a half an hour ride in a month.
I've read that if you hook up to the terminals under the hood, you get more power directly to the starter. You get some power loss going through that 10' of monster cable from the battery. Also, not to beat a dead horse, thinner jumper cables just don't deliver the same power as thicker ones.
If jumping had always gotten it going before, that does sound like it's not the starter.
You driving patterns just may be it, though. You say that if you don't get to it in 2-3 days it's weaker. I believe that a battery can be 2.5 years old and still have a problem...especially if it's in a constantly weak state. If it was the fsr, you'd have a dead battery in a day from what I hear...certainly in 2.
You live in the city, so it's not unreasonable to think that this is all from your driving patterns. I don't know if a battery can be permanently damaged from being in a continually undercharged state...
Next step I'd suggest after you get it started, is to get the battery load tested or replaced. If you got a 49DL, I know you have a prorated warranty still. If not, go back to where you got it and get it tested at least.
When you get it going, either go on a long drive or right to the battery store.
And I'm tl...dr again...but try to lift up the cables on the battery, check ground cable for tightness...look for corrosion...tighten nut under +terminal cap and ground lug. Easy to do and free and you wouldn't be the first with such a basic issue.
As desperate as this sounds, in comedy, 'likes' and 'views,' 'friends,' and 'retweets' really help. If I've ever helped you, please help me by friending, liking, viewing, and retweeting. It makes others think I have a following...it'll take you a minute or less. If you could, I'd really appreciate it!
A recent set--NSFW audio: https://youtu.be/_dcxcZfD6dg
Mangofy your E46!