Garage roof structure

Need to replace 30 garage door rollers. Ebay has the nylon wheel type for one quarter the cost at the big box stores. I am sure they both are made in Asia. Anyone have performance history with nylon rollers purchased from ebay? Thanks in advance.

Mom's garage door is a solid wood (16'x7' I think). It has a front torsion spring set mounted to the door header. Both torsion springs were replaced sometime in the last 2 years due to one spring breaking. At the time, the tech commented that the door was really too heavy should be replaced. Last week, the center bracket for the spring mechanism ripped out of the wall and the springs unwound quite spectacularly (based on the amount of plaster dust spread over the car inside the garage). The bar came out of one of the end brackets as well. I tried to lift the door to get the car out until the tech could get there but even two adults couldn't budge it. Tech came out and made the repair by mounting the center bracket and setting the bar end back in the bracket. Again, the comment was that the door is too heavy and should be replaced. Note the the spring replacement and the bracket replacement were done by two different companies. My thoughts on this is that the house/garage is over 50 years old so this door and spring arrangement can't be all bad. I suspect that while the door is heavy, there is more than a little bit of sales going on here. The bracket that came out of the wall had fairly short lag bolts (less than 2") holding it to the wall. Considering that the wall is finished plaster, I suspect the screws were put in by the last technician and were too short to adequately reach the wood door header. It is an all brick house so I suppose it is possible that shorter bolts were needed but I don't think so. Mom is considering replacing the door if it fails again while she owns it (1-3 years, max.). I think if this was a good repair, it should last 5-10 years (newer springs and a solid bracket) but if it does fail, I say don't replace the door. My question is: Solid wood doors are still sold and serviced today so why would an older one be too heavy? - Peter