You worry too much.Boas can go a very long time without signs, yes, but it's not that common for them to go for their whole life without showing signs. They usually start showing some problems (or more) within the time frame you have suggested. Whether it be as simple a problems shedding, eating, or whatever.
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Boas look up all the time. They are special like that.A ceiling light, or a fan (or whatever) will make some boas gawk at them. Others do it for no reason. They just do it sometimes. Stargazing is very much different than just looking up. It's quite awkward looking. You would know it when you see it.
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You, and your snakes are fine. No sweat.![]()