Whether it's 3, 4 or 5. It's just not enough.
As a pax who pays for F I do not want to wait 3 days for the next flight where F is available because I happened to need an additional day of work abroad.

Seriously, imagine you buy a fullfare F tix ZRH-SIN-ZRH at >10k CHF right? You intend to fly back from your meetings in Singapore, like I always do, Friday evening. Then for whatever reason, you need a little bit more time in the city, and you need to fly back on Saturday. That happens! Then they tell you, sorry Mr. fullfare paying HON, the next flight that has availability in F is on Wednesday...because we have only 3 seats in the cabin. Who accepts that??? Definitely not me.