Hey guys... I feel like I cannot keep the phone on for more that 72 hours continuously.
I'm using Galaxy SII. Currently everything original (no custom rom/kernel)
I believe that most of Android phones have the same problem.

After 50 hours++ of up time of the phone (I mean the phone keeps on for 50 hours), The phone will become noticeable lag, but just a bit, not too much. One of the best evidence is in the game Fruit Ninja. I will feel the lag everytime I slash the fruit.
I'm sure that most apps is closed (except background apps like samsung keypad) and my battery usage graph is in straight horizontal line (without any optimize software, only with BetterBatteryStats). Only 500 - 600MB of RAM is used and I think this is normal.
After I restart the phone, the phone will become smooth and the RAM will be 300 - 400MB used only. Others do not show any difference.
And sure, the phone will repeat the same problem after some hours.

I wish I can keep the phone on continuously and no need to restart it frequently just like normal phones.

Can someone share some experience about this?
Is there any solution for this?
Or this is the nature of Android?
Can Custom ROM solve this?

I am new to Android and I am deciding whether or not I should root my phone.

The only reason I want to root my Arc S is to remove the FB application. Cant tahan see it running on the phone when I dont use FB. It takes up my precious 4mb

But since ICS is going to be out soon, I want to have ICS too, I dont know, can I upgrade to ICS if I root my phone. Or must I unroot it back.

Thanks! I will try and root and see

google