I think I’m up to two false positives after six years, neither of which was in any way important (in fact, I kinda agreed with its judgement), and I’m up to 175 false negatives in the last 5⅓ years (of which 32 are from the last twelve months, which suggests a fairly steady rate across the whole time; it comes to about one every eleven days).
Before that, I used Gmail (on the same address, for about six years), and my memory is that its false positive rates were around one every month or two, and some of them actually mattered; and its false negative rates varied: sometimes it’d go for a few months with none, then it might let through one or two per day for a few weeks. Certainly less consistent. In the last year I’ve also had to use Gmail via a couple of organisations on addresses with very low volume (less than one per day) which have never received any spam, and both have had at least two false positives.
Before that, I used Gmail (on the same address, for about six years), and my memory is that its false positive rates were around one every month or two, and some of them actually mattered; and its false negative rates varied: sometimes it’d go for a few months with none, then it might let through one or two per day for a few weeks. Certainly less consistent. In the last year I’ve also had to use Gmail via a couple of organisations on addresses with very low volume (less than one per day) which have never received any spam, and both have had at least two false positives.