As they're from COCA, I'm not your best respondent. I'd say the first was dubious; 'has been' would be clearer. The second is OK; the context shows that this relates to a recurring fixture, which the 49ers always lose - so it means 'they have been losing it for 50 years'. In the third, in Br English, I'd expect a past continuous - 'has been losing...for...'.
But I defer to the locals!
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