Can an iPhone battery get weaker and weaker?

[WhySoSeriouss]

I've had my iPhone 3G for about 2 years now and just recently in the past 4 days, the battery has been getting drained really quickly.

I turned on Facebook the other day when I was out and it said "20% of battery remaining" and I couldn't see the screen properly so on SB settings I turned the brightness to full and literally less than 20 seconds later it popped up with "10% of battery remaining"

I charged it up last night and used it to text 2 people and download a small game from Cydia and the battery is on 75% (I downloaded a battery percentage metre from Cydia like the one on the 3Gs)

I always go on SB settings and make sure theres always free space quite often and I don't use push notifications, push mail, bluetooth or location either and my brightness is always on about 20%

Anyone had similar problems?

Thanks.

[CaptainChaos]

It is very possible that your battery is going out, but I would look at everything you have installed via Cydia. You may want to do a restore to see if it helps. The first route for me is always getting rid of Cydia stuff first.

[screamforme02]

it does and mine is dying faster and faster every day. yeah iphone 4 i also dropeed mine in some water its a sad day in my iphone life