#1 and #2 were fine but #3 went nuts! She did have issues with her ovaries though and both have recently been removed at rising 7! all three had foals at around 4 (don't know their origins that well just know they had foals).
I did have one that was awful with seasons, but she turned out to have cancerous overies. Sadly the operation was not successful as she died after the removal (internal infection). A pity as she was lovely and quite the most talented horse I ever did sit on.
No, of all the mares we have had most you don't even notice, a couple were a bit sharp/needy around their seasons but that wasn't just at 5, it was every time they were in season from youngsters until they got older !
They start coming into season as yearlings even if they don't show it so if your mare has previously been fine then became noticeable bad then I would be investigating why she is now not doing so well. As above she could have cysts or tumors.
When I bought my mare last year as a rising 5 year old and she had her first season with me I did think "What have I done"?!!!
I think a lot of her apparently 'seasonal' behaviour was actually due to the fact that she was stressed and unhappy at the yard we were on. I have moved her home now and she is much more chilled and happy, and the only real sign of a season is a lift of the tail when you scratch her bum ðŸ˜
I can tell when The Beast is in season because she gets a bit more squealy and daft when you go to catch her, either doesn't want to be caught or has to have a run around/buck/rear/play first... like a giant spring lamb. And she's a dreadful flirt with any available gelding (or sometimes inanimate objects like the wheelbarrow). But her behaviour when being handled and ridden behaviour hardly changes. Just turns into a big daft doofus in the field. Lol.
My last 3 mares all went from no mareish traits at 4 to being more mareish or at minimum noticeable seasons at 5. That said, none were 'nutty' with it. Still work well under saddle but more flirty when they see a handsome boy!