It was my first trip from Bangalore to Guntur. Nice experience while travelling in bus, but at the halt station the food is not good & as well as not hygienic, also not cost worthy. But some part of the road while travelling caused inconvenience as the route is not good. As I travelled during night time and I'm a first time traveller from Bangalore to Guntur, I don't know where the routes are bad. I think the bus went through kadapa. I suggest you to choose the bus route via Tirupati. The kadapa roads caused inconvenience. Expected one or more pit stops. Reached the destination happily with 1 hour delay of the mentioned time.
Keeping my travel experience in mind, i would suggest you to carry homemade food items while planning your journey.