what is the ideal battery life for Iphone 5s?

There is no such animal. There is only an estimated average life - 1,000 full charge cycles. How long that takes depends entirely on the amount of "off charger" use.

That will depend on what you do with the phone, signal strength, temperature and settings. It going to vary.

eljockey wrote:

I mean how meany hours usage

Will vary tremendously from person to person depending on how quickly they use up a charge and thus how often they have to recharge. That's why battery life is always given in estamted number of full discharge/charge cycles. People will go through a cycle at very different rates - some may only experience a single full cycle over a couple or even few days if they are light users. A really heavy user may go through a couple of full cycles every day.