Back in the mists of time, I had the same teacher for 4 school years (ages 6-10)
It was a tiny village school, with 2 year groups in a class; I was put up a year when we moved to the area which was more than ok academically, but bullying problems in that first year meant my DPs "moved" me back down (I had the same desk, and the work was all as one group or workbooks for eg maths, just wasn't sitting with the ringleader any more) at the start of the second year, so in the younger half of the class for 2 years; then the top half, once. Then they reshuffled the years and she had junior 2-3 rather than junior 1-2 (told you it was a while back) so we had each other for another year.
I would think less of Mrs R if she wasn't as glad to see the back of me as I was of her by the end of it, but I went on to pass a "10+" into a selective prep when we moved again, so something obviously stuck! (Probably by mere repetition, I had multiples of the same art projects by the end, let alone other subjects!)
I had a different "same teacher" for 3 out of 5 years at secondary, and one for the whole of 6th form too, but somehow less obvious later on - probably as subject teaching is separate anyway.
I suppose I turned out to be fairly academic in the end though. I got a decent raft of GCSE/A levels, 2 degrees and a few other postgrad bits and bobs, now back at uni in my 30s alongside a FT job; a reasonable group of mates, nice flat and a DBoyf. I don't suppose it did me too much harm in the long term.
And I can make a mean sugar-paper sheep, possibly in my sleep!