What to do if your backpack and bags break/rip?

[blackughal]

Should you just buy garbage bags? or duct tape it back together?

[JAdaken]

I always have a needle and thread and a roll of duct tape. Fabric glue would be good to have packed too.

[max lift]

if the tare is on a seam I would take it down to a seamstress or a shoe repair shop and have them stitch it if its that the fabric is very warn and starting to give way maybe its time for a new pack,

It its a problem on the trail duct tape saves the day every time,

[AlbinoGerbil]

I always have a needle and thread and a roll of duct tape. Fabric glue would be good to have packed too.

I second that. I usually carry about 30 yards of heavy duty nylon thread and 3-5 med-large needles for self repair. I also carry a small tube of 'Fabritac' (fabric glue) as well as a small roll(30-50 yds) of industrial strength duct tape.
I've also found that if you have the load bearing seems reinforced before use it goes a long way to increasing the life expectency of any bag.