Settle this for me...

[Sage]

Buddy and I both make wine from our own vines.

I add prescribed amount of yeast nutrients, shy tablespoon, about the 3rd day of fermentation. (5 gallons of must)

He adds a table spoon per day every day until he presses. (5 gallons of must)

I think he's flirting with off flavors.

 

[cmason1957]

Well he is leaving lots of good food for any spoilage bacteria, that is for certain.

 

[1d10t]

YAN requirement for the yeast also comes into play. We may like to over think and over due our hobbies but more is not always better. I've read the reason there is a V3 of this calculator is that people were complaining of off flavors in small batches because of excessive nutrient additions.
https://www.meadmaderight.com/tosna.html

 

[user 36973]

I add prescribed amount of yeast nutrients, shy tablespoon, about the 3rd day of fermentation. (5 gallons of must)

Running through the dosing here:
5 gallons must -> ~3 gallons wine (11.4L)
So, 1 tbsp DAP (~15g) addition is about 1.3g/L. DAP is 20% nitrogen, so you are adding about 260ppm nitrogen, which is in the good dosage range, depending on the yeast needs and your incoming YAN in the must.

He adds a table spoon per day every day until he presses. (5 gallons of must)

I would certainly not add more than what you've added without being certain I'm addressing a known issue. Your friend has potentially added 5x more nitrogen than needed. When the yeast is done, there will be plenty of nitrogen left over to feed the next opportunistic spoilage organism. Might help to remind your friend that wine is not the end state for the biological processes that act on grapes (we just try to keep wine as the end state)