Receiving consumes very little power; transmitting consumes a lot of power.
Refer to the owner's manual for theoretical use time per charge.
Most such data is idealistic, not realistic,
so don't expect anywhere near the time claimed. *
A second battery pack would be a very good idea,
especially if it can be charged without being attached to the radio.
One of the best things to get, if it is offered for a particular model,
is a battery case for AA cells.
Typically, HTs burn through alkaline cells like the Cookie Monster inhales cookies --
but at least you'd have an option that would provide some usability
in the absence of a functional rechargeable pack.
* In December 2011, I bought a Kenwood TH-K2AT and an AA case for it.
So far, at best, I've normally gotten about 2/3 of the use time claimed in the manual
with either the PB43N NiMH pack or AA cells.
If you haven't yet done so, contact a local amateur radio operator or two
(or a club) and get some advice about things.
>> It's best to learn any hobby from others' mistakes
rather than having to make all the same ones yourself!
73
KJ6QKV