How far can pasture meadow fertility drop before it affects equestrian centre prestige?

From spring to autumn you can keep 100% fertility by rotating daily with only twice the acreage required for pasture, but I wasn't sure if this is actually necessary? It also doesn't work for winter.

I'm wondering what the best rotation strategy is in winter?

I guess this is more of a strategy question than a gameplay question so please let me know if that's not allowed.

Thank you in advance