My rear left regulator failed on Friday. I ordered the parts and as soon as they're in I'll get it fixed. I nearly always drive with the windows down, so they get used very frequently. Due to this, it's important to me to pro-actively replace them. They don't appear to be that hard to replace, and for $100 delivered it's worth it to me to pro-actively do them.
I'll do them one at a time to spread the cost, but I definitely would be pro-active. Just keeping duct tape doesn't really help since you have to take the door apart and do half the job to get the glass back up. And it's embarrassing to have a plastic trash bag over my broken window for a week.
