Laptop battery

[Monoriu]

I am generally very happy with my laptop.  I primarily use it to play music at home, and for web browsing and anime watching when I am travelling.  I don't use it to play games, so I don't really need too much computing power.  The problem is that the battery life seems to be getting shorter every passing month.  It used to last 4 hours or so.  Now it is barely two and a half hours.  The laptop also seems to have problem detecting the battery with increasing frequency.  I also want a bigger SSD as my music collection grows (currently 128GB).

My question is, is it worth it to replace the battery and buy a bigger SSD (256GB SSD is US$200-250 inclding data transfer)?  Or should I buy a new laptop? I am inclined to just do the minimum to extend the life of the laptop to save money.

CPU is i5-2467M, RAM is 6GB, Windows 7.