No thats not normal, it should last abit longer.

I have the newer n95 8gb and it lasts about 2 maybe 3 days with texts and a few short calls.

You can get batterys on amazon for £2-3 but it doesnt say whether its a nokia one or not.

To be honest in 1.5 years ive never thought the battery was shit considering the amount of tasks the phone can do.