Nokia Nseries :: 6700 Slide Boot-up Duration?

I am planning to purchase a Nokia 6700 slide for my mother, however, the seller has stated that it takes a long time to start up, anything between 5 minutes to an hour; and often varies. I am wondering what is casuing the problem with the device before purchasing, other than the start-up time, everything on the handset works perfectly fine (according to the seller).

Would reinstalling the operating system be of any solution? From what I know, there are no other faults for the device, and the boot up error occured totally randomly. This boot- up time is the only fault on the phone; and could be a problem, as my mother may be unable to charge the device at various points, where the phone would turn off due to low battery.

Or are there any other steps which I could take to ensure that this problem doesn't occur? Also, this is an old phone, therefore it is out of warranty.