when to start reducing nutrient strength

for a 8-9 week strain, when should I start to taper off the nutes? I was thinking after 4-5 weeks start reducing.

I guess it's up to personal preference.

You could experiment with it and see which gives better yield/quality.

Personally, I feel the shit out of my plants and then flush the last 2 weeks.
You can use an EC meter to measure how much your plants can take, and push them to the limit

too early, reduce at week 8