As with most things you pay your money and you get what you pay for.
Run time is not just dependent on the current rating of the battery, more important is the quality of the motor and batteries.
I went out to do a job last week with my 14V De Walt and believe me they do run out of power
. The customer insisted I used his 24V drill rather than swap the battery, unfortunately I don't remember the make but he got it from one of the sheds.
It was rubbish, terrible control of speed, snapping heads off and at the same time it was a lot less powerful than the 14V DW.
A drill driver will be the most useful power tool you will buy and, unless you are only planning to do the very occasional bit of diy, I would save up and get a branded model a 12V may well be sufficient.
You won't be sorry