Is there a way to determine if thread is good? I have read that fluorescent light can damage it but what if its been sealed in original packaging in a box? Any help would be appreciated. I would say the strength was similar to 8-10 lb test mono

8-10 pounds seems like an awful lot to me, although I've never tested breaking strength. I wouldn't worry about it personally. The thread is more or less reinforcement of the epoxy, if I understand things correctly. Kind of like the rebar in concrete or the fibers in fiberglass resin. Carbon fiber is another example in the auto and cycling world. Essentially a carbon fiber reinforced plastic of sorts. Someone more knowledgeable step in if I'm wrong.

Some tread will loose strength over time it depends on how it was stored ,the brand, color etc. I keep mine in a cabinet with drawers and don't leave it out when I'm not using it. I used some 30 year old Holland thread that worked fine but I've had some become unuseable after just a few years. One brands turquoise seems to go bad fairly quickly for some reason. Some colors fade on the top layers too even though it's kept in the dark. Once it's on the rod it doesn't matter but wrapping with it can be a headache.